Dynamic control of fluid pressure within fluid flow circuit

Abstract

The invention relates to dynamic control of fluid pressure within a fluid flow circuit. A system and method for dynamically controlling fluid pressure within a fluid flow circuit is disclosed. The fluid circulation system supplies working fluid through the inlet line and returns the returned working fluid through the outlet line. A fluid management device is fluidly coupled to the inlet line and the outlet line. The fluid management device defines a pressure control point. A first proportional valve and a first pressure sensor are disposed in the inlet line to selectively adjust and measure inlet fluid pressure in the inlet line. A second proportional valve and a second pressure sensor are disposed in the outlet line to selectively adjust and measure outlet fluid pressure in the outlet line. The controller is configured to maintain the inlet fluid pressure at a target inlet pressure and to maintain the outlet fluid pressure at a target outlet pressure.

Description

Technical Field

[0001] The present disclosure relates generally to fluid flow circuits, and more particularly to dynamically controlling fluid pressure of a fluid management device. Background Art

[0002] Fluid flow circuits (e.g., those used in inkjet printing systems) typically include a pressure control device to control the pressure within the circuit. However, controlling the pressure within a fluid flow circuit used on a complex three-dimensional surface can be difficult because the orientation and position (e.g., height) of the pressure control device may change relative to the fluid source during operation.

[0003] Existing methods of controlling pressure at controlled points within a fluid flow loop employ two centrally located pumps for pressure regulation at a single point of flow impedance. However, such conventional methods lack the flexibility to manage pressure and fluid flow at more than one point, and create stability issues because the pumps are relatively far away from the controlled points. Other methods involve many centrally placed pressure actuators connected by tubes to convert each controlled pressure to its desired position. These alternative methods may be suitable for high pressure scenarios or low density fluid systems, but are inadequate for low pressure systems (such as inkjet printing systems) with high density fluids where the hydraulic head cannot be ignored. Summary of the invention

[0004] The subject matter of the present application has been developed in response to the prior art, and specifically, in response to problems with and needs that have arisen from or have not yet been fully addressed by fluid flow circuits of fluid management systems. In general, the subject matter of the present application has been developed to provide a fluid flow circuit that overcomes at least some of the above-mentioned shortcomings of the prior art. The system herein provides high precision, low range control of more than one independent pressure point supplied by a centralized fluid circulation system. The resulting control performance provides higher bandwidth and precision control compared to known methods of low-range incompressible fluid pressure control systems. The system can be used for inkjet printing on flat or curved surfaces, and in embodiments, inkjet printing on curved surfaces on transportation equipment such as aircraft, ships, automobiles, etc.

[0005] A system for dynamically controlling fluid pressure in a fluid flow circuit is disclosed herein. The system includes an inlet pipeline and an outlet pipeline. The system also includes a fluid circulation system configured to supply a working fluid through the inlet pipeline and return the returned working fluid through the outlet pipeline. The system also includes a fluid management device fluidically coupled to the inlet pipeline and the outlet pipeline. The fluid management device defines a pressure control point, and the fluid management device is selectively movable relative to the fluid circulation system. The system also includes a first proportional valve disposed in the inlet pipeline and configured to selectively adjust the inlet fluid pressure in the inlet pipeline between the first proportional valve and the fluid management device. The system also includes a first pressure sensor disposed between the first proportional valve and the fluid management device and configured to measure the inlet fluid pressure in the inlet pipeline. The system also includes a second proportional valve disposed in the outlet pipeline and configured to selectively adjust the outlet fluid pressure in the outlet pipeline between the fluid management device and the second proportional valve. The system also includes a second pressure sensor between the fluid management device and the second proportional valve and configured to measure the outlet fluid pressure in the outlet pipeline. In addition, the system includes a controller operably coupled to the first proportional valve, the first pressure sensor, the second proportional valve, and the second pressure sensor. The controller is configured to control the first proportional valve so that the inlet fluid pressure is maintained at a target inlet fluid pressure, and to control the second proportional valve so that the outlet fluid pressure is maintained at a target outlet fluid pressure. The foregoing subject matter of this paragraph characterizes Example 1 of the present disclosure.

[0006] The first proportional valve and the second proportional valve are actuatable independently of each other.The foregoing subject matter of this paragraph characterizes Example 2 of the present disclosure, wherein Example 2 also includes the subject matter according to Example 1 described above.

[0007] Each of the first proportional valve and the second proportional valve is a direct-acting proportional valve. The foregoing subject matter of this paragraph characterizes Example 3 of the present disclosure, wherein Example 3 also includes the subject matter according to any one of Examples 1 to 2 described above.

[0008] The fluid pressure within the fluid flow circuit does not exceed 50 pounds per square inch (PSI).The foregoing subject matter of this paragraph characterizes Example 4 of the present disclosure, wherein Example 4 also includes the subject matter according to any one of Examples 1 to 3 described above.

[0009] The system is configured to automatically compensate for inertial effects and hydraulic head.The foregoing subject matter of this paragraph characterizes Example 5 of the present disclosure, wherein Example 5 also includes the subject matter according to any one of Examples 1 to 4 described above.

[0010] The working fluid is an incompressible fluid. The foregoing subject matter of this paragraph characterizes Example 6 of the present disclosure, wherein Example 6 also includes the subject matter according to any one of Examples 1 to 5 described above.

[0011] The fluid management device includes at least one nozzle fluidly coupled to the inlet line and the outlet line and configured to distribute the working fluid. The foregoing subject matter of this paragraph characterizes Example 7 of the present disclosure, wherein Example 7 also includes the subject matter according to any one of Examples 1 to 6 described above.

[0012] The working fluid is ink. The fluid management device is a print head configured to dispense ink. The foregoing subject matter of this paragraph characterizes Example 8 of the present disclosure, wherein Example 8 also includes the subject matter according to Example 7 described above.

[0013] The fluid circulation system includes a pump that is selectively operable to supply working fluid to the inlet line and return the return working fluid from the outlet line. The foregoing subject matter of this paragraph characterizes Example 9 of the present disclosure, wherein Example 9 also includes the subject matter according to any one of Examples 1 to 8 described above.

[0014] The fluid circulation system includes a supply reservoir for supplying the working fluid and a return reservoir for storing the returned working fluid. The foregoing subject matter of this paragraph characterizes Example 10 of the present disclosure, wherein Example 10 also includes the subject matter according to any one of Examples 1 to 9 described above.

[0015] The system includes a plurality of fluid management devices, a plurality of inlet pipelines, a plurality of outlet pipelines, a plurality of first proportional valves, a plurality of second proportional valves, a plurality of pressure control points, a plurality of first pressure sensors, and a plurality of second pressure sensors. Each of the plurality of fluid management devices is connected to a corresponding one of the plurality of inlet pipelines and a corresponding one of the plurality of outlet pipelines. Each of the plurality of fluid management devices defines a corresponding one of the plurality of pressure control points, and each of the pressure control points is different from any other one of the pressure control points. Each of the first proportional valves is disposed in a corresponding one of the plurality of inlet pipelines, and each of the plurality of first pressure sensors is located between a corresponding one of the plurality of first proportional valves and a corresponding one of the plurality of fluid management devices. Each of the second proportional valves is disposed in a corresponding one of the plurality of outlet pipelines, and each of the plurality of second pressure sensors is located between a corresponding one of the plurality of fluid management devices and a corresponding one of the plurality of second proportional valves. The aforementioned subject matter of this paragraph characterizes Example 11 of the present disclosure, wherein Example 11 also includes the aforementioned subject matter according to any one of Examples 1 to 10.

[0016] The plurality of fluid management devices are independently and selectively movable relative to the fluid circulation system.The foregoing subject matter of this paragraph characterizes Example 12 of the present disclosure, wherein Example 12 also includes the subject matter according to Example 11 described above.

[0017] The first proportional valve is configured to adjust the inlet fluid pressure based on feedback from the first pressure sensor. The second proportional valve is configured to adjust the outlet fluid pressure based on feedback from the second pressure sensor. The aforementioned subject matter of this paragraph characterizes Example 13 of the present disclosure, wherein Example 13 also includes the aforementioned subject matter according to any one of Examples 1 to 12.

[0018] The controller adjusts the first proportional valve and the second proportional valve to maintain a desired average fluid pressure and a desired fluid flow rate of the working fluid at the fluid management device between the inlet fluid pressure and the outlet fluid pressure. The foregoing subject matter of this paragraph characterizes Example 14 of the present disclosure, wherein Example 14 also includes the foregoing subject matter according to any one of Examples 1 to 13.

[0019] The first proportional valve is disposed in the inlet pipeline adjacent to the fluid management device. The second proportional valve is disposed in the outlet pipeline adjacent to the fluid management device. The aforementioned subject matter of this paragraph characterizes Example 15 of the present disclosure, wherein Example 15 also includes the aforementioned subject matter according to any one of Examples 1 to 14.

[0020] The present invention also discloses an inkjet printing system. The inkjet printing system includes an inlet pipeline and an outlet pipeline. The inkjet printing system also includes an ink circulation system, which is configured to supply ink through the inlet pipeline and return undistributed ink through the outlet pipeline. The inkjet printing system also includes a print head, which includes at least one nozzle, the at least one nozzle is fluidically connected to the inlet pipeline and the outlet pipeline and is configured to distribute ink. The print head defines a pressure control point and is selectively movable relative to the ink circulation system. The inkjet printing system also includes a first proportional valve, which is arranged in the inlet pipeline and is configured to selectively adjust the inlet fluid pressure in the inlet pipeline between the first proportional valve and at least one nozzle. The inkjet printing system also includes a first pressure sensor, which is between the first proportional valve and the print head and is configured to measure the inlet fluid pressure in the inlet pipeline. The inkjet printing system also includes a second proportional valve, which is arranged in the outlet pipeline and is configured to selectively adjust the outlet fluid pressure in the outlet pipeline between at least one nozzle and the second proportional valve. The inkjet printing system also includes a second pressure sensor, which is between the print head and the second proportional valve and is configured to measure the outlet fluid pressure in the outlet pipeline. In addition, the inkjet printing system includes a controller operably connected to the first proportional valve, the first pressure sensor, the second proportional valve, the second pressure sensor and the print head. The controller is configured to control the first proportional valve so that the inlet fluid pressure is maintained at a target inlet fluid pressure, and to control the second proportional valve so that the outlet fluid pressure is maintained at a target outlet fluid pressure. The controller is configured to control at least one nozzle to selectively distribute ink onto a surface. The aforementioned subject matter of this paragraph characterizes Example 16 of the present disclosure.

[0021] The first proportional valve is disposed in an inlet pipeline proximate to the print head. The second proportional valve is disposed in an outlet pipeline proximate to the print head. The foregoing subject matter of this paragraph characterizes Example 17 of the present disclosure, wherein Example 17 also includes the subject matter according to Example 16 described above.

[0022] The first proportional valve and the second proportional valve are actuatable independently of each other.The foregoing subject matter of this paragraph characterizes Example 18 of the present disclosure, wherein Example 18 also includes the subject matter according to any one of Examples 16 to 17 described above.

[0023] The print head is a piezoelectric print head. The foregoing subject matter of this paragraph characterizes Example 19 of the present disclosure, wherein Example 19 also includes the subject matter according to any one of Examples 16 to 18 described above.

[0024] The present invention also discloses a method for dynamically controlling fluid pressure within a fluid flow circuit. The method includes determining a target inlet fluid pressure in an inlet line supplying a working fluid to a fluid management device. The method also includes determining a target outlet fluid pressure in an outlet line returning the working fluid from the fluid management device based on a desired average fluid pressure of the working fluid at the fluid management device and a desired pressure differential at the fluid management device. The method also includes controlling the inlet fluid pressure by actuating a first proportional valve to maintain the target inlet fluid pressure. The inlet fluid pressure is measured by a first pressure sensor. The method also includes controlling the outlet fluid pressure by actuating a second proportional valve to maintain the target outlet fluid pressure. The outlet fluid pressure is measured by a second pressure sensor. The foregoing subject matter of this paragraph characterizes Example 20 of the present disclosure.

[0025] The described features, structures, advantages and / or characteristics of the subject matter of the present disclosure may be combined in one or more examples, including embodiments and / or implementations, in any suitable manner. In the following description, many specific details are provided to give a thorough understanding of the examples of the subject matter of the present disclosure. Those skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced in the absence of one or more of the specific features, details, parts, materials and / or methods of a particular example, embodiment or implementation. In other cases, additional features and advantages may be recognized in certain examples, embodiments and / or implementations that may not be present in all examples, embodiments or implementations. In addition, in some cases, known structures, materials or operations are not shown or described in detail to avoid blurring the various aspects of the subject matter of the present disclosure. According to the following description and the appended claims, the features and advantages of the subject matter of the present disclosure will become more completely apparent, or can be learned by the practice of the subject matter as described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be presented by reference to specific examples shown in the accompanying drawings. It should be understood that these drawings depict only typical examples of the subject matter and that they are not to be considered limiting of its scope. The subject matter will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0027] Figure 1 is a schematic diagram of a fluid flow circuit for a fluid management system according to one or more examples of the present disclosure;

[0028] Figure 2 is a schematic diagram of another example of a fluid flow circuit for a fluid management system according to one or more examples of the present disclosure;

[0029] Figure 3is a schematic diagram of an inkjet printing system according to one or more examples of the present disclosure; and

[0030] Figure 4 is a schematic flow chart of a method of dynamically controlling fluid pressure within a fluid flow circuit according to one or more examples of the present disclosure. DETAILED DESCRIPTION

[0031] References throughout this specification to "one example," "example," or similar language mean that a particular feature, structure, or characteristic described in conjunction with the example is included in at least one example of the subject matter of the present disclosure. The phrases "in one example," "in an example," and similar language throughout this specification may, but do not necessarily, all refer to the same example. Similarly, use of the term "embodiment" means an embodiment having a particular feature, structure, or characteristic described in conjunction with one or more examples of the subject matter of the present disclosure, however, an embodiment may be associated with one or more examples without an explicit correlation to indicate otherwise.

[0032] Examples of fluid flow circuits for fluid pressure control systems are disclosed herein. Some features of at least some examples of fluid flow circuits are provided below. In some examples, the fluid flow circuit may form part of a pressure control fluid system that requires precise control of the pressure of a low-pressure fluid within a fluid management device. In other examples, the fluid flow circuit may form part of a fluid management device that dispenses a working fluid. For example, the fluid flow circuit may be from a portion of an inkjet printing system configured to dispense ink onto a surface. Reference to the entire inkjet printing system is intended only to illustrate one application of a dynamic fluid pressure control system for a fluid flow circuit. The systems and methods disclosed herein are particularly suitable for complex three-dimensional applications, where the orientation of a fluid management device of a fluid flow circuit may change during operation. For example, an inkjet printing system for printing on a three-dimensional surface, such as a surface of an aircraft, is disclosed. The fluid flow circuit includes a fluid management device having a nozzle from which a working fluid (e.g., ink) is dispensed. The systems and methods disclosed herein dynamically manage both an inlet fluid pressure upstream of the fluid management device and an outlet fluid pressure downstream of the fluid management device. The inlet fluid pressure and the outlet fluid pressure are regulated to ensure that a target fluid pressure is always maintained at the nozzle regardless of the orientation of the fluid management device.

[0033] Reference Figure 1, the system 100 includes a fluid management device 102. In some examples, the fluid management device 102 is coupled to a structure (not shown) that allows the fluid management device 102 to selectively move translationally in at least one direction (e.g., forward / backward, left / right, or up / down) and rotate in at least one degree of freedom (e.g., pitch, yaw, and roll). In some examples, the fluid management device 102 is supported by the structure for rotation in three degrees of freedom, such as rotation around the X, Y, and Z axes of a standard coordinate system. In some examples, the structure may be an industrial multi-axis robotic arm.

[0034] The fluid management device 102 is configured to have a working fluid flow through the fluid management device 102. In some examples, the fluid management device 102 is configured to dispense the working fluid from the fluid management device 102. Therefore, in some examples, the fluid management device 102 includes at least one nozzle 110 through which the working fluid is dispensed. As used herein, the working fluid includes any incompressible fluid (i.e., a fluid that is relatively resistant to volume change when subjected to pressure) that can be dispensed from the fluid management device 102. For example, the working fluid can be water or a water-based fluid, an oil or an oil-based fluid, a hydraulic fluid, ink, etc. In some examples, the fluid management device 102 may include a plurality of nozzles 110. For example, the fluid management device 102 may have up to one hundred nozzles configured to dispense the working fluid. In other examples, the fluid management device 102 may have up to one thousand nozzles configured to dispense the working fluid. The plurality of nozzles may be configured to dispense the working fluid simultaneously and evenly relative to each other. Alternatively, one or more of the plurality of nozzles may be configured to be independently controlled relative to one or more other of the plurality of nozzles such that one or more of the nozzles may dispense fluid at different times or at different rates relative to other of the nozzles.

[0035] In other examples, the fluid management device 102 does not dispense the working fluid from the fluid management device 102, and therefore does not have a nozzle, but rather precisely controls the pressure of the working fluid within the fluid management device 102. For example, the fluid management device 102 can be a pressure-based haptic device. That is, a pressure-based haptic device is configured to use changes in fluid pressure to control the force feedback experienced by a user. Such a device has practical applications in different fields such as robotic-assisted manufacturing, virtual and augmented reality environments, and telepresence systems.

[0036] The fluid management device 102 defines a pressure control point 112 that controls the pressure. In the case where the fluid management device 102 includes a nozzle 110, the pressure control point 112 is defined at each of the one or more nozzles 110 of the fluid management device 102, so that the pressure at at least one nozzle 110 is controlled. As used herein, a pressure control point refers to a specific location within a system or device where the pressure of the fluid is actively and independently regulated or controlled. This point serves as a reference or focal point for pressure management, ensuring that the pressure at this specific location remains consistent and can be adjusted separately from other points within the system as needed. A given system may have a single pressure control point 112 or multiple pressure control points. Because the pressure control point 112 is defined by the fluid management device 102, each nozzle 110 of a fluid management device 102 having multiple nozzles 110 will have the same pressure control point 112. Therefore, the pressure at each nozzle 110 of a fluid management device 102 having multiple nozzles 110 remains consistent and controlled.

[0037] The system 100 also includes a fluid circulation system 104 configured to circulate a working fluid through the fluid management device 102. That is, the fluid circulation system 104 is configured to supply the working fluid to and from the fluid management device 102 at a continuous and controlled flow rate. The system 100 includes an inlet line 106 that serves as an entry point for the working fluid into the fluid management device 102 and fluidly couples the fluid circulation system 104 to the fluid management device 102 to supply the working fluid from the fluid circulation system 104. Similarly, the system 100 includes an outlet line 108 that serves as a return path for the working fluid, is independent of the inlet line 106, and fluidly couples the fluid circulation system 104 to the fluid management device 102 to return the working fluid to the fluid management device 102. In some examples, the returned working fluid is undispensed working fluid that is not dispensed from the nozzle 110 of the fluid management device 102. In view of the foregoing, the inlet line 106 and the outlet line 108 of the system 100 are fluidly coupled to the at least one nozzle 110 of the fluid management device 102 .

[0038] In some examples, such as Figure 2As shown, the fluid circulation system 104 includes a pump 124 that is selectively operable to supply the working fluid to the inlet line 106 and return the working fluid from the outlet line 108. In addition, in some examples, the fluid circulation system 104 includes a supply reservoir 126 for supplying the working fluid to the inlet line 106 and a return reservoir 128 for storing the returned working fluid. In some examples, the pump 124 is configured between the return reservoir 128 and the supply reservoir 126 to move the working fluid from the return reservoir 128 to the supply reservoir 126, thereby allowing the returned working fluid to recirculate through the fluid circulation system 104.

[0039] The system 100 also includes a proportional value to dynamically control the fluid pressure at the fluid management device 102. That is, and returning to reference Figure 1 , the pressure control point 112 of the fluid management device 102 is controlled by using a dual proportional valve, one of which is provided in the inlet line 106 and one is provided in the outlet line 108. The first proportional valve 114 is provided in the inlet line 106 and is configured to selectively adjust the inlet fluid pressure in the inlet line 106 between the first proportional valve 114 and the nozzle 110. Similarly, the second proportional valve 118 is provided in the outlet line 108 and is configured to selectively adjust the outlet fluid pressure in the outlet line 108 between the nozzle and the second proportional valve 118. The first proportional valve 114 and the second proportional valve 118 are valves for precisely adjusting the fluid flow rate (i.e., fluid difference) and the average fluid pressure of the working fluid. In some examples, the first proportional valve 114 and the second proportional valve 118 operate by changing the valve opening in proportion to the applied electric or electronic control signal. That is, the first proportional valve 114 and the second proportional valve 118 can provide fine-tuning control of the fluid flow rate and the average fluid pressure at a level that is proportional to the input signal received from the controller, as described below. Therefore, it should be understood that the first proportional valve 114 and the second proportional valve 118, which are operable to produce an average fluid pressure and a fluid flow rate at the fluid management device 102, can control the fluid pressure at the nozzle 110. In addition, the fluid management device 102 includes an internal fluid passage (not shown) that fluidly links the inlet line 106 and the outlet line 108 to the nozzle 110, such that the inlet line 106 and the outlet line 108 are directly linked to the nozzle 110.

[0040] The first proportional valve 114 and the second proportional valve 118 can be actuated independently of each other. That is, the control or adjustment of one valve does not affect the control or adjustment of the other valve because each valve is individually controllable. For example, the inlet fluid pressure can be increased or decreased by the first proportional valve 114 while maintaining the outlet fluid pressure constant, and vice versa. This flexibility allows fine-tuning control of the fluid flow rate and average fluid pressure at the fluid management device 102. In addition, the first proportional valve 114 and the second proportional valve 118 are direct-acting proportional valves. In other words, each proportional valve is directly controlled by the input signal it receives from the controller, thereby allowing the position or opening of the valve to be adjusted immediately in response to the input signal. Therefore, the first proportional valve 114 and the second proportional valve 118 are directly actuated by the controller without amplification or intermediate mechanism involved in the valve's response to the signal. In this way, the first proportional valve 114 and the second proportional valve 118 respond directly and proportionally to the input signal received from the controller. When the input signal changes, the valves accurately adjust their position or opening to achieve the desired fluid flow rate or average fluid pressure, thereby allowing fine-tuning control in the system 100. In this way, the first proportional valve 114 and the second proportional valve 118 allow high control performance of the working fluid. Unlike systems that rely on pumps that adjust fluid pressure by adjusting the flow through a fixed opening (i.e., fixed impedance), the first proportional valve 114 and the second proportional valve 118 achieve precise control by adjusting the flow impedance through the valve (i.e., variable impedance). That is, by directing the adjustment of the flow impedance through the valve, the fluid pressure and flow rate of the system 100 can be adjusted.

[0041] The first proportional valve 114 is disposed in the inlet line 106 in close proximity to the fluid management device 102. Similarly, the second proportional valve 118 is disposed in the outlet line 108 in close proximity to the fluid management device 102. This allows the working fluid flowing through the inlet line 106 and the outlet line 108 to be modulated as close to the fluid management device 102 as possible, thereby reducing the distance that the working fluid travels between the nozzle 110 and the proportional valves. By locating the first proportional valve 114 and the second proportional valve 118 in close proximity to the fluid management device 102, there is minimal working fluid between the pressure control point 112 and the valves. Thus, this minimization reduces the impact of inertial effects on fluid pressure originating from machine motion or other external disturbances. The control performance of the system 100 improves the closer the proportional valves (and the pressure sensors discussed below) are to the fluid management device 102.

[0042] In some examples, as used herein, a proportional valve is in close proximity to the structure of the fluid management device 102 when the proportional valve is as close as possible to the structure of the fluid management device 102 without interfering with the function, assembly, and / or installation of the proportional valve, the fluid management device 102, or the pressure sensor, as described below. In some examples, the first proportional valve 114 and the second proportional valve 118 are within 300 mm of the structure of the fluid management device 102. In other examples, the first proportional valve 114 and the second proportional valve 118 are between 150 mm and 300 mm of the structure of the fluid management device 102. In contrast, due to practical challenges that arise when using a pump to regulate fluid pressure, a pump from a system that relies on a pump to regulate fluid pressure cannot be as close to the fluid management device as a proportional valve. Typically, pumps used to regulate fluid pressure require a pulse dampener to eliminate pressure fluctuations in the working fluid as the working fluid enters or leaves the pump. These pulse dampeners tend to be relatively large and contain a large amount of working fluid, thereby increasing the amount of working fluid between the pump and the pressure control point, and generally cannot completely eliminate fluid pressure pulses. Therefore, using a pump to regulate fluid pressure not only increases the number of components in the system due to the additional pulsation dampener, but control performance is also affected because the pump lacks the responsiveness of a proportional valve.

[0043] The system 100 also includes a first pressure sensor 116 between the first proportional valve 114 and the fluid management device 102 for determining an actual pressure of the working fluid in the inlet line 106. The first pressure sensor 116 is configured to generate an inlet line pressure signal indicating an actual pressure of the working fluid supplied to the nozzle 110 through the inlet line 106. The first proportional valve 114 is configured to adjust the inlet fluid pressure based on feedback from the first pressure sensor 116. Similarly, the system 100 includes a second pressure sensor 120 between the fluid management device 102 and the second proportional valve 118 for determining an actual pressure of the working fluid in the outlet line 108. The second pressure sensor 120 is configured to generate an outlet line pressure signal indicating an actual pressure of the working fluid removed from the nozzle 110 through the outlet line 108. The second proportional valve 118 is configured to adjust the outlet fluid pressure based on feedback from the second pressure sensor 120.

[0044] The system 100 also includes a controller 122 operably coupled to the first proportional valve 114, the first pressure sensor 116, the second proportional valve 118, and the second pressure sensor 120. The controller 122 is configured to control the first proportional valve 114 so that the inlet fluid pressure is maintained at a target inlet fluid pressure, and to control the second proportional valve 118 so that the outlet fluid pressure is maintained at a target outlet fluid pressure. The controller 122 may represent any kind of computing device of a controller, or may also be part of another device, such as a device completely included in a server, and portions of the controller 122 may be located elsewhere or in other computing devices. More specifically, the controller 122 includes a processor that can execute logic stored in a data storage device to control the operation of the controller 122. In some examples, the controller 122 is configured to send an electronic control signal to the first proportional valve 114 of the second proportional valve 118 to control the actuation of the valve.

[0045] The controller 122 is programmed to dynamically control a desired average fluid pressure (e.g., meniscus pressure) at the nozzle 110 of the fluid management device 102. That is, the controller 122 sends a signal for adjusting the first proportional valve 114 and the second proportional valve 118 to maintain a desired average fluid pressure of the working fluid at the nozzle 110 between the inlet fluid pressure and the outlet fluid pressure. Thus, the controller 122 is configured to maintain the average fluid pressure of the working fluid under certain conditions so that it does not exceed the surface tension at the nozzle 110 and causes air to be drawn into the nozzle 110 or causes the working fluid to be uncontrollably dispensed from the nozzle 110. In addition, the controller 122 is also programmed to dynamically control the pressure difference (i.e., fluid flow rate) between the inlet fluid pressure and the outlet fluid pressure. In some examples, the controller 122 may determine a target inlet fluid pressure and a target outlet fluid pressure to maintain the target pressure difference at the nozzle 110. The controller 122 can control the first proportional valve 114 and the second proportional valve 118 to achieve a target inlet fluid pressure and a target outlet fluid pressure, respectively, to provide a target pressure differential at the nozzle 110, regardless of the orientation of the fluid management device 102. Importantly, this configuration ensures reliable performance even when the orientation of the system changes, by dynamically calculating and compensating for the hydraulic head between the first pressure sensor 116 and the second pressure sensor 120 and the pressure control point 112 when calculating the inlet fluid pressure and the outlet fluid pressure, respectively.

[0046] The controller 122 is also programmed to control the first proportional valve 114 based on the inlet line pressure signal from the first pressure sensor 116, and to control the second proportional valve 118 based on the outlet line pressure signal from the second pressure sensor 120. In some examples, the target pressure differential is in the range of approximately +2 mbar to -2 mbar. In other examples, the target pressure differential is in the range of approximately +1 mbar to -1 mbar. In addition, the controller 122 is at least partially used to maintain the fluid pressure within the fluid flow circuit at no more than 50 pounds per square inch (PSI).

[0047] The controller 122 is configured to automatically compensate for inertial effects (i.e., resistance of the working fluid due to a change in the state of motion of the working fluid) by adjusting the first proportional valve 114 and / or the second proportional valve 118 to account for the inertial effects. Similarly, the controller 122 is configured to automatically compensate for hydraulic head, i.e., pressure exerted by the working fluid due to its height relative to a reference point, by adjusting the first proportional valve 114 and / or the second proportional valve 118 based on a reference point to account for changes in fluid pressure due to a change in the height or height of the working fluid. Thus, the controller 122 can automatically compensate to account for changes in fluid motion and / or changes in fluid pressure due to height differences to maintain precise control of fluid flow and fluid pressure even when fluid motion or fluid height changes.

[0048] In fact, if Figure 1 As shown, fluid management device 102 receives working fluid from fluid circulation system 104 and selectively distributes the working fluid to a surface from at least one nozzle 110. Nozzle 110 defines a desired average fluid pressure at which the working fluid is present in nozzle 110 to accurately distribute the working fluid to a surface.

[0049] refer to Figure 2 , in some examples, the system 100 has multiple fluid management devices 102, such as fluid management device 102A having nozzle 110A, up to fluid management device 102N having nozzle 110N. The system 100 is not limited to the two fluid management devices shown, and may include any number of fluid management devices (as shown by the vertical points extending between the shown components). Thus, the system 100 can be used for high-precision, low-range control of more than one independent pressure point supplied by the centralized fluid circulation system 104. That is, each fluid management device 102A-102N has an independent pressure point controlled by a corresponding proportional valve and pressure sensor. The system 100 is able to control pressure at many different locations of different fluid management devices 102A-102N and automatically compensate for inertial effects and hydraulic head.

[0050] Each of the plurality of fluid management devices 102A-102N is coupled to a corresponding one of the plurality of inlet pipelines 106A-106N and a corresponding one of the plurality of outlet pipelines 108A-108N. In addition, each of the plurality of inlet pipelines 106A-106N and outlet pipelines 108A-108N has a corresponding one of the proportional valves 114A-114N and the proportional valves 118A-118N and a corresponding one of the pressure sensors 116A-116N. For example, the fluid management device 102A is coupled to the inlet pipeline 106A having the first proportional valve 114A and the first pressure sensor 116A and the outlet pipeline 108A having the second proportional valve 118A and the second pressure sensor 120A. Similarly, the fluid management device 102N is coupled to the inlet pipeline 106N having the first proportional valve 114N and the first pressure sensor 116N and the outlet pipeline 108N having the second proportional valve 118N and the second pressure sensor 120N. Fluid circulation system 104 is configured to supply working fluid through inlet lines 106A-106N and return working fluid through outlet lines 108A-108N. Thus, the working fluid supplied to fluid management devices 102A-102N originates from the same working fluid source (eg, fluid circulation system 104).

[0051] Each of the plurality of fluid management devices 102A-102N defines a corresponding one of the plurality of pressure control points 112A-112N associated with the plurality of nozzles 110A-110N. That is, each of the fluid management devices 102A-102N defines a pressure control point that is different from any other pressure control point of another of the fluid management devices 102A-102N. Thus, each of the fluid management devices 102A-102N is independently and selectively movable relative to the fluid circulation system 104. At least one of the fluid management devices 102A-102N is configured to be spaced apart a vertical distance from at least another of the fluid management devices 102A-102N during operation of the system 100. Thus, the controller 122 or controllers (not shown) are configured to compensate for height variations, such as hydraulic heads, between the fluid management devices as described above.

[0052] like Figure 3 As shown, in some examples, the fluid management device of system 200 is a print head 202 configured to distribute ink on a surface 201. In some examples, surface 201 is a three-dimensional surface of an aircraft, and print head 202 is configured to distribute ink on the three-dimensional surface of the aircraft by moving and / or rotating relative to the three-dimensional surface when printing on the three-dimensional surface. In some examples, print head 202 is a piezoelectric print head.

[0053] The ink circulation system 204 is configured to supply ink through an inlet line 206 and return undispensed ink through an outlet line 208. The ink in the ink circulation system 204 includes one color of ink. That is, at least one nozzle 210 of the printhead 202 is configured to dispense ink having one color of ink from the ink circulation system 204 on the surface 201. Therefore, multiple colors of ink can be printed on the surface 201 using multiple printheads that are fluidly coupled to other ink circulation systems.

[0054] The ink circulation system 204 further includes a first proportional valve 214, a second proportional valve 218, a first pressure sensor 216, and a second pressure sensor 220, which are used to dynamically control the average fluid pressure (e.g., meniscus pressure) of the print head 202 and the pressure difference at the nozzle 210, as described above. The ink circulation system 204 further includes a controller 222, which is operably connected to the first proportional valve 214, the first pressure sensor 216, the second proportional valve 218, and the second pressure sensor 220 to maintain the inlet fluid pressure at a target inlet fluid pressure and maintain the outlet fluid pressure at a target outlet fluid pressure. The controller 222 is also configured to control at least one nozzle 210 to selectively dispense ink onto the surface 201.

[0055] refer to Figure 4 , according to some examples, a method 300 for dynamically controlling fluid pressure within a fluid flow circuit is shown. The method 300 includes (block 302) determining a target inlet fluid pressure in an inlet line 106 supplying a working fluid to a fluid management device 102. In some examples, the fluid management device includes a nozzle 110 configured to dispense the working fluid. Additionally, in some examples, the working fluid is an ink configured to be dispensed (i.e., printed) on a surface (such as an aircraft surface). The method 300 also includes (block 304) determining a target outlet fluid pressure in an outlet line 108 returning from the nozzle 110 based on a desired average pressure of the working fluid at the fluid management device 102 and a desired pressure differential (i.e., fluid flow rate) at the fluid management device 102. The method 300 also includes (block 306) controlling the inlet fluid pressure by actuating a first proportional valve 114 to maintain the target inlet fluid pressure. The inlet fluid pressure is measured by a first pressure sensor 116 between the first proportional valve 114 and the fluid management device 102. The method 300 also includes (block 308 ) controlling the outlet fluid pressure to maintain the target outlet fluid pressure by actuating the second proportional valve 118 . The external fluid pressure is measured by a second pressure sensor 120 between the second proportional valve 118 and the fluid management device 102 .

[0056] In the above description, certain terms may be used, such as "upper", "lower", "up", "lower", "horizontal", "vertical", "left", "right", "upper", "lower", etc. These terms are used to provide some clear description when dealing with relative relationships where applicable. However, these terms are not intended to imply absolute relationships, positions and / or orientations. For example, with respect to an object, an "upper" surface can simply become a "lower" surface by turning the object over. However, it is still the same object. In addition, unless otherwise expressly stated, the terms "include", "comprise", "have" and their variations mean "including but not limited to". Unless otherwise expressly stated, an enumerated list of items does not mean that any or all items are mutually exclusive and / or mutually inclusive. Unless otherwise expressly stated, the terms "one", "an" and "the" also refer to "one or more". In addition, the term "multiple" can be defined as "at least two".

[0057] In addition, examples of an element "coupled" to another element in this specification may include direct and indirect coupling. Direct coupling may be defined as an element that is coupled to another element and in some contact with the other element. Indirect coupling may be defined as a coupling between two elements that are not in direct contact with each other, but have one or more additional elements between the coupled elements. In addition, as used herein, fixing an element to another element may include direct fixing and indirect fixing. In addition, as used herein, "adjacent" does not necessarily mean contact. For example, an element may be adjacent to another element without contacting the element.

[0058] As used herein, when used with a list of items, the phrase "at least one of" means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. An item may be a specific object, thing, or category. In other words, "at least one of" means that any combination of the items or number of items in the list may be used, but all of the items in the list may not be required. For example, "at least one of item A, item B, and item C" may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of item A, item B, and item C" may mean, for example, but not limited to, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0059] Unless otherwise indicated, the terms "first," "second," etc. are used herein merely as labels and are not intended to impose order, position, or hierarchical requirements on the items to which these terms refer. Furthermore, reference to, for example, a "second" item does not require or preclude the presence of, for example, a "first" or lower numbered item and / or, for example, a "third" or higher numbered item.

[0060] As used herein, a system, device, structure, article, element, component, or hardware that is "configured to" perform a specified function is indeed capable of performing the specified function without any changes, rather than having only the potential to perform the specified function after further modification. In other words, for the purpose of performing a specified function, a system, device, structure, article, element, component, or hardware that is "configured to" perform a specified function is specifically selected, created, implemented, utilized, programmed, and / or designed. As used herein, "configured to" represents an existing characteristic of a system, device, structure, article, element, component, or hardware that enables the system, device, structure, article, element, component, or hardware to perform a specified function without further modification. For the purposes of this disclosure, a system, device, structure, article, element, component, or hardware that is described as "configured to" perform a specific function may be additionally or alternatively described as "suitable for" and / or "operable to" perform the function.

[0061] The schematic flow chart included herein is generally described as a logical flow chart. Therefore, the order depicted and the steps of the marking indicate an example of the method presented. It is conceivable that other steps and methods that are equivalent to one or more steps or parts thereof of the method shown in function, logic or effect. In addition, the format and symbols adopted are provided to explain the logical steps of the method, and are understood to not limit the scope of the method. Although various arrow types and line types can be adopted in the flow chart, they are understood to not limit the scope of the corresponding method. In fact, some arrows or other connectors can be used to indicate only the logical flow of the method. For example, an arrow can indicate a waiting or monitoring period of unspecified duration between the enumeration steps of the method depicted. In addition, the order in which a particular method occurs may or may not strictly follow the order of the corresponding steps shown.

[0062] Without departing from the spirit or essential characteristics of the present subject matter, the present subject matter may be embodied in other specific forms. The described examples are considered in all respects to be illustrative only and not restrictive. All changes within the meaning and scope of equivalents of the examples herein should be included within their scope.

Claims

1. A system (100) for dynamically controlling fluid pressure in a fluid flow circuit, the system comprising: an inlet pipeline (106) and an outlet pipeline (108); a fluid circulation system (104) configured to supply working fluid through the inlet line (106) and return the returned working fluid through the outlet line (108); a fluid management device (102), wherein the fluid management device (102) defines a pressure control point (112), and wherein the fluid management device (102) is selectively movable relative to the fluid circulation system (104); a first proportional valve (114) disposed in the inlet line (106) and configured to selectively adjust an inlet fluid pressure in the inlet line (106) between the first proportional valve (114) and the fluid management device (102); a first pressure sensor (116) located between the first proportional valve (114) and the fluid management device (102) and configured to measure the inlet fluid pressure in the inlet line (106); a second proportional valve (118) disposed in the outlet line (108) and configured to selectively adjust an outlet fluid pressure in the outlet line (108) between the fluid management device (102) and the second proportional valve (118); a second pressure sensor (120) located between the fluid management device (102) and the second proportional valve (118) and configured to measure the outlet fluid pressure in the outlet line (108); and A controller (122) is operatively coupled to the first proportional valve (114), the first pressure sensor (116), the second proportional valve (118), and the second pressure sensor (120), wherein the controller (122) is configured to control the first proportional valve (114) such that the inlet fluid pressure is maintained at a target inlet fluid pressure, and to control the second proportional valve (118) such that the outlet fluid pressure is maintained at a target outlet fluid pressure.

2. The system (100) according to claim 1, wherein: The first proportional valve (114) and the second proportional valve (118) are actuatable independently of each other.

3. The system (100) of claim 1, wherein: Each of the first proportional valve (114) and the second proportional valve (118) is a direct-acting proportional valve.

4. The system (100) of claim 1, wherein: The fluid pressure within the fluid flow circuit does not exceed 50 pounds per square inch PSI.

5. The system (100) of claim 1, wherein: The system (100) is configured to automatically compensate for inertial effects and hydraulic head.

6. The system (100) of claim 1, wherein: The working fluid is an incompressible fluid.

7. The system (100) of claim 1, wherein: The fluid management device (102) includes at least one nozzle (110) fluidly coupled to the inlet line (106) and the outlet line (108) and configured to distribute the working fluid.

8. The system (100) according to claim 7, wherein: The working fluid is ink; and The fluid management device (102) includes a printhead (202) configured to dispense the ink.

9. The system (100) of claim 1, wherein: The fluid circulation system (104) also includes a pump (124) that is selectively operable to supply the working fluid to the inlet line (106) and return the returned working fluid from the outlet line (108).

10. The system (100) of claim 1, wherein: The fluid circulation system (104) further includes: a supply reservoir (126) for supplying the working fluid; and a return reservoir (128) for storing the returned working fluid.

11. The system (100) of claim 1, further comprising: A plurality of fluid management devices (102), a plurality of inlet pipelines (106), a plurality of outlet pipelines (108), a plurality of first proportional valves (114), a plurality of second proportional valves (118), a plurality of pressure control points (112), a plurality of first pressure sensors (116), and a plurality of second pressure sensors (120), wherein: Each of the plurality of fluid management devices (102) is coupled to a corresponding one of the plurality of inlet lines (106) and a corresponding one of the plurality of outlet lines (108); Each of the plurality of fluid management devices (102) defines a corresponding one of the plurality of pressure control points (112), and each of the plurality of pressure control points (112) is different from any other one of the pressure control points (112); Each of the plurality of first proportional valves (114) is disposed in a corresponding one of the plurality of inlet pipelines (106), and each of the plurality of first pressure sensors (116) is disposed between a corresponding one of the plurality of first proportional valves (114) and a corresponding one of the plurality of fluid management devices (102); and Each of the plurality of second proportional valves (118) is disposed in a corresponding one of the plurality of outlet pipelines (108), and each of the plurality of second pressure sensors (120) is between a corresponding one of the plurality of fluid management devices (102) and a corresponding one of the plurality of second proportional valves (118).

12. The system (100) according to claim 11, wherein: The plurality of fluid management devices (102) are independently and selectively movable relative to the fluid circulation system (104).

13. The system (100) of claim 1, wherein: The first proportional valve (114) is configured to regulate the inlet fluid pressure based on feedback from the first pressure sensor (116); and The second proportional valve (118) is configured to regulate the outlet fluid pressure based on feedback from the second pressure sensor (120).

14. The system (100) of claim 1, wherein: The controller (122) adjusts the first proportional valve (114) and the second proportional valve (118) to maintain a desired average fluid pressure and a desired fluid flow rate of the working fluid at the fluid management device (102) between the inlet fluid pressure and the outlet fluid pressure.

15. The system (100) of claim 1, wherein: The first proportional valve (114) is disposed in the inlet line (106) adjacent to the fluid management device (102); and The second proportional valve (118) is disposed in the outlet line (108) proximate to the fluid management device (102).

16. An inkjet printing system (200), the inkjet printing system comprising: an inlet line (206) and an outlet line (208); an ink circulation system (204) configured to supply ink through the inlet line (206) and return undispensed ink through the outlet line (208); a printhead (202) comprising at least one nozzle (210) fluidly coupled to the inlet line (206) and the outlet line (208) and configured to dispense ink, wherein the printhead (202) defines a pressure control point (212), and wherein the printhead (202) is selectively movable relative to the ink circulation system (204); a first proportional valve (214) disposed in the inlet line (206) and configured to selectively adjust an inlet fluid pressure in the inlet line (206) between the first proportional valve (214) and the at least one nozzle (210); a first pressure sensor (216) between the first proportional valve (214) and the print head (202) and configured to measure the inlet fluid pressure in the inlet line (206); a second proportional valve (218) disposed in the outlet pipeline (208) and configured to selectively adjust an outlet fluid pressure in the outlet pipeline (208) between the at least one nozzle (210) and the second proportional valve (218); a second pressure sensor (220) between the print head (202) and the second proportional valve (218) and configured to measure the outlet fluid pressure in the outlet line (208); and A controller (222) operatively connected to the first proportional valve (214), the first pressure sensor (216), the second proportional valve (218), the second pressure sensor (220), and the print head (202), wherein the controller (222) is configured to control the first proportional valve (214) so ​​that the inlet fluid pressure is maintained at a target inlet fluid pressure, and to control the second proportional valve (218) so that the outlet fluid pressure is maintained at a target outlet fluid pressure, and wherein the controller (222) is configured to control the at least one nozzle to selectively dispense ink onto a surface (201).

17. The inkjet printing system (200) of claim 16, wherein: The first proportional valve (214) is disposed in the inlet pipeline (206) adjacent to the print head (202); and The second proportional valve (218) is disposed in the outlet line (208) adjacent to the print head (202).

18. The inkjet printing system (200) of claim 16, wherein: The first proportional valve (214) and the second proportional valve (218) are actuatable independently of each other.

19. The inkjet printing system (200) of claim 16, wherein: The print head (202) is a piezoelectric print head.

20. A method (300) for dynamically controlling fluid pressure within a fluid flow circuit, the method (300) comprising: determining (302) a target inlet fluid pressure in an inlet line supplying working fluid to a fluid management device (102); determining (304) a target outlet fluid pressure in an outlet line returning working fluid from the fluid management device (102) based on a desired average fluid pressure of the working fluid at the fluid management device (102) and a desired fluid flow rate at the fluid management device (102); controlling (306) an inlet fluid pressure by actuating a first proportional valve to maintain the target inlet fluid pressure, wherein the inlet fluid pressure is measured by a first pressure sensor; and The outlet fluid pressure is controlled (308) by actuating a second proportional valve to maintain the target outlet fluid pressure, wherein the outlet fluid pressure is measured by a second pressure sensor.

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