Print fluid recirculation system and method

Abstract

In one example of the disclosure, a system for print fluid recirculation includes a supply manifold, a recirculation manifold, a printbar, and a recirculation path. The printbar includes a plurality of printheads in fluid communication with the supply manifold and the recirculation manifold. The recirculation path is in fluid connection with the supply manifold and the recirculation manifold and enables print fluid to recirculate through the plurality of printheads at a controlled flow rate.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to printing fluid recirculation systems and methods. BACKGROUND

[0002] Printers can apply printing fluid to paper or another substrate to produce an image. One example of a printer is an inkjet printing system (e.g., a thermal print inkjet printer or a piezoelectric print inkjet printer) in which printing fluid is applied directly to a substrate using multiple groups of printheads. In other examples, inkjet printheads can be used to apply printing fluid to a blanket or other intermediate transfer member, which will come into contact with a substrate and thereby deliver the printing fluid to the substrate. SUMMARY

[0003] A printing fluid recirculation system comprising: a first supply manifold; a first recirculation manifold; a first printbar comprising a first plurality of printheads in fluid communication with one another, in fluid communication with the first supply manifold, and in fluid communication with the first recirculation manifold; a second supply manifold; a second recirculation manifold; a second printbar comprising a second plurality of printheads in fluid communication with one another, in fluid communication with the second supply manifold, and in fluid communication with the second recirculation manifold; a supply manifold bridge enabling fluid communication of printing fluid between the first supply manifold and the second supply manifold; and a recirculation path in fluid communication with the first supply manifold, the first recirculation manifold, the second supply manifold, and the second recirculation manifold, the recirculation path enabling recirculation of printing fluid through the first plurality of printheads and the second plurality of printheads at a controlled flow rate. BRIEF DESCRIPTION OF DRAWINGS

[0004] Figure 1 is a block diagram depicting an example of a system for printing fluid recirculation.

[0005] Figure 2 is a block diagram depicting another example of a system for printing fluid recirculation.

[0006] Figure 3 is a block diagram depicting another example of a system for printing fluid recirculation.

[0007] Figure 4 is a block diagram depicting another example of a system for printing fluid recirculation.

[0008] Figure 5 is a block diagram of memory resources and processing resources that depict an example of a method for printing fluid recirculation.

[0009] Figure 6 is a simple schematic diagram illustrating an example of a system for print fluid recirculation.

[0010] Figure 7 is a simple schematic diagram illustrating an example of a system for print fluid recirculation including an electronic pressure regulator component.

[0011] Figure 8 is a simple schematic diagram illustrating an example of a system for print fluid recirculation for multiple print bars fluidly connected to one another.

[0012] Figure 9 is a simple schematic diagram illustrating an example of a system for print fluid recirculation for multiple print bars fluidly connected to one another including an electronic pressure regulator component.

[0013] Figure 10 is a simple schematic diagram illustrating another example of a system for print fluid recirculation for multiple print bars fluidly connected to one another and arranged at the same height.

[0014] Figure 11 is a bottom view of print bars, a supply manifold, and a recirculation manifold fluidly connected to one another in an example system for print fluid recirculation.

[0015] Figure 12A and Figure 12B is provided a perspective view of a supply manifold in an example system for print fluid recirculation.

[0016] Figure 12C and Figure 12D is provided a perspective view of a recirculation manifold in an example system for print fluid recirculation.

[0017] Figure 13 is a bottom view of print bars, a supply manifold, and a recirculation manifold fluidly connected to one another in another example system for print fluid recirculation.

[0018] Figure 14 is a flow diagram depicting an implementation of an example of a method for print fluid recirculation.

[0019] Figure 15 is a flow diagram depicting an implementation of another example of a method for print fluid recirculation. DETAILED DESCRIPTION

[0020] For many conventional inkjet printing systems, during certain printing operations, printing fluid is pushed through the printheads, but during non-printing operations, printing fluid does not circulate within or between the printheads. Lack of printing fluid circulation can present significant challenges for long-term operation. Printhead nozzles are prone to drawing in air between print jobs, causing the residual printing fluid in the nozzles to dry out. Dried-out printing fluid can cause serious print quality problems and can damage the printhead, such that the printhead will need to be replaced. Replacing a printhead involves not only material costs, but also productivity costs during printer downtime.

[0021] Some inkjet printing systems schedule and execute printhead spit routines as maintenance operations to prevent ink in the nozzles from drying out. Typically, during a spit routine, the printheads eject printing fluid into a sponge and / or spittoon between print jobs. However, for certain printers and print jobs, spit routines present significant costs. Such costs can include the expense of printing fluid and consumables (e.g., sponges) consumed and printer downtime associated with user replacement of spit routine consumables or emptying of the spittoon. Moreover, in some cases, spit operations can cause printing fluid to miss the consumable sponge or spittoon, causing other print quality or printer damage issues.

[0022] To address these issues, various examples described in greater detail below provide a new system and method that enables automated printing fluid recirculation at a printer. In an example, a printing fluid recirculation system includes a supply manifold, a recirculation manifold, and a recirculation path. A printbar includes a set of printheads that are in fluid communication with each other, in fluid communication with the supply manifold, and in fluid communication with the recirculation manifold. The recirculation path is in fluid connection with the supply manifold and the recirculation manifold and enables printing fluid to be recirculated through the set of printheads at a controlled and consistent flow rate.

[0023] In an example, the printing fluid recirculation system can include a first vacuum source and a vacuum regulator. The first vacuum source is in fluid communication with the recirculation manifold and is used to cause negative pressure to be applied to the recirculation manifold. The vacuum regulator is in fluid communication with the recirculation manifold, the first vacuum source, and a second vacuum source. The vacuum regulator, together with the second vacuum source, is used to regulate the negative pressure applied to the recirculation manifold by the first vacuum source. In an example, the printing fluid recirculation system can include a control engine to control the first vacuum source and the vacuum regulator to provide a consistent target vacuum pressure as printing fluid moves through the set of printheads.

[0024] In an example, the printing fluid recirculation system can include a reservoir. In an example, the first vacuum source can be a recirculation pump and is used to pump printing fluid that has passed through the recirculation manifold and the vacuum regulator into the reservoir. In an example, the recirculation path can include a supply pump in fluid connection with the reservoir. In these examples, the supply pump is used to pump printing fluid from the reservoir to the supply manifold.

[0025] In an example, the printing fluid recirculation system can include an electronic pressure regulator component in fluid communication with the vacuum regulator and the second vacuum source and positioned between the vacuum regulator and the second vacuum source. The electronic pressure regulator component is used to provide a pilot pressure to the vacuum regulator.

[0026] In an example, the recirculation path can include a recirculation isolation valve in fluid communication with the recirculation manifold and the reservoir. The recirculation isolation valve is used to enable movement of printing fluid from the recirculation manifold to the reservoir when the recirculation isolation valve is open. The recirculation isolation valve disables movement of printing fluid from the recirculation manifold to the reservoir when the recirculation isolation valve is closed. In an example, movement of printing fluid along the jet operation printing fluid return path during a printing fluid jet operation is not prevented when the recirculation isolation valve is closed.

[0027] In an example, the printing fluid recirculation system can provide printing fluid recirculation between a plurality of print bars, each print bar having its own set of printheads. An example of a printing fluid recirculation system can include a plurality of supply manifolds and a plurality of recirculation manifolds.

[0028] Users of inkjet printing systems will appreciate the avoidance of print quality issues and equipment damage that often result from printing fluid in the printheads drying out between printing fluid jet operations. In implementations, the disclosed systems and methods should greatly reduce the number of purging operations performed. Utilization of the disclosed printing fluid recirculation systems and methods should result in a significant reduction in printhead replacement and printer downtime. Customer satisfaction with inkjet printers utilizing the disclosed systems and methods will be enhanced, resulting in increased installation and utilization of such inkjet printers.

[0029] Figure 1is a block diagram depicting an example of a system 100 for print fluid recirculation. The print fluid recirculation system 100 includes a supply manifold 102, a recirculation manifold 104, and a print bar 106. The print bar 106 includes a set of printheads 108 that are in fluid communication with each other, in fluid communication with the supply manifold 102, and in fluid communication with the recirculation manifold 104. As used herein, a “supply manifold” generally refers to a pipe, tube, or chamber that receives print fluid through an entry opening via a connected pipe and branches into or connects to a number of dispensing openings through which print fluid is supplied to a set of printheads. As used herein, a “recirculation manifold” generally refers to a pipe, tube, or chamber that branches into or connects to a number of collection openings through which print fluid is received from a set of printheads and has a delivery opening through which print fluid is moved to a recirculation path via a connected pipe. In various examples, the supply and / or recirculation manifolds can include valves or interfaces to an electronic network for controlling movement of print fluid through the manifolds.

[0030] As used herein, a “print bar” generally refers to an element or structure that holds a set of printheads. In examples, a print bar can hold a set of printheads where each printhead will eject print fluid of the same color or other attribute. As used herein, a “printhead” generally refers to a mechanism for ejecting a liquid, such as a print fluid. Examples of printheads are drop-on-demand inkjet printheads, such as piezoelectric printheads and thermal resistive printheads. As used herein, a “print fluid” generally refers to any liquid that can be applied by a printer to a substrate during a printing operation, such as a print fluid ejection operation, including but not limited to ink, primer, and overcoat (e.g., varnish), water, and solvents other than water. As used herein, “ink” generally refers to a liquid to be applied to a substrate during a printing operation, such as a print fluid ejection operation, to form an image on the substrate. As used herein, primer generally refers to a substance that is applied to a substrate as a preparatory coating before ink or another imaging print fluid is applied to the substrate.

[0031] The system 100 includes a recirculation path 110 that is fluidly connected with the supply manifold 102 and the recirculation manifold 104. As used herein, a first component is “fluidly connected” or “fluidly connected to” a second component generally means that the first and second components are connected such that fluid can flow from the first component to the second component or from the second component to the first component. The recirculation path 110 enables print fluid to be recirculated through a set of printheads 108 at a controlled and consistent flow rate. In an example, the recirculation path 110 includes a pipe, conduit, or tube, and fluid connections can be established via the pipe, conduit, or tube. In an example, the recirculation path can include other elements, such as a vacuum regulator, an electronic pressure regulator component, a recirculation isolation valve, and / or a recirculation pump.

[0032] In a particular example of the printing recirculation system 100, a first printbar is used to eject a first color of print fluid, and a second printbar is used to eject a second color of print fluid. In this example, a first recirculation path is fluidly connected with a first supply manifold and a first recirculation manifold, and is used to enable print fluid of the first color to be recirculated through the first printbar at a controlled consistent flow rate. In this example, a second recirculation path is fluidly connected with a second supply manifold and a second recirculation manifold, and is used to enable print fluid of the second color to be recirculated through the second printbar at a controlled consistent flow rate. In this way, the disclosed system 100 can enable different colors of print fluid between color-specific printheads to be automatically recirculated.

[0033] In some examples, a printhead can include an internal pressure regulator to regulate the flow rate of print fluid from the supply manifold into the printhead. The printhead can also include an internal check valve at an outlet of the printhead that is used to prevent print fluid from traveling from the recirculation manifold to the printhead when the recirculation path is activated, but to allow print fluid to travel from the printhead to the recirculation manifold. The internal regulation of the printhead provided by these components can facilitate a balance of positive pressure to the nozzles that eject print fluid with a vacuum pressure that pulls un-ejected print fluid through the check valve and into the recirculation manifold.

[0034] In some examples, when the recirculation path is closed, the printing fluid will travel through the supply manifold(s) of the printbar(s) and back to the reservoir, completely bypassing the printhead. In examples, when the recirculation path is open, some of the printing fluid will travel along the path, but another portion of the printing fluid will travel through the printhead and into the recirculation path and back to the reservoir. In examples, when printing fluid is being ejected during a printing operation, the internal pressure regulator of the printhead allows more printing fluid to flow through the printhead as printing fluid is ejected, while the vacuum pressure at the outlet of the printhead remains constant to maintain a constant (or within a certain range or tolerance) flow of printing fluid away from the printhead during printing or non-printing operations. In examples, the printhead internal pressure regulation system can be used to balance or regulate positive and negative pressure events at the nozzles of the printhead, where a lack of such balancing or regulation can result in printing defects, uneven thermal behavior, and de-priming of the nozzles.

[0035] Figure 2 is a block diagram depicting another example of a system 100 for printing fluid recirculation. This example is similar to Figure 1 the example of FIG. 1, except that the recirculation path 110 includes a vacuum regulator 212 and a first vacuum source 320. The first vacuum source is in fluid communication with the recirculation manifold 104 and is used to cause a negative pressure to be applied to the recirculation manifold. The vacuum regulator 212 is in fluid communication with the recirculation manifold, the first vacuum source, and a second (sometimes referred to herein as a “secondary”) vacuum source 214. The vacuum regulator 212, together with the second vacuum source 214, is used to regulate the negative pressure applied to the recirculation manifold by the first vacuum source 320.

[0036] In examples, each of the first vacuum source 320 and the second vacuum source 214 can be or include any component or system for applying a negative pressure to the recirculation path. In examples, the vacuum sources can be, but are not limited to, mechanical vacuum pumps or Venturi-type vacuum generators. As used herein, a “vacuum regulator” generally refers to any device that maintains a desired vacuum pressure in a system. In examples, the vacuum regulator 212 can be a suction regulator, a back pressure regulator, or a spring-operated regulator. In examples, the vacuum regulator 212 can influence the vacuum pressure within the system 100 by limiting the flow between the first vacuum source 320 and the recirculation manifold 104, and in this way precisely control the vacuum to a target flow rate. In examples, while the vacuum regulator 212 controls the vacuum pressure, the vacuum regulator 212 does not allow air or other gases to enter the system 100. In examples, the vacuum regulator 212 can influence the vacuum pressure within the system 100 by controlling or limiting the vacuum provided by the multiple vacuum sources.

[0037] Figure 3is a block diagram depicting another example of a system 100 for print fluid recirculation. This example is similar to Figure 2 except that the system includes a reservoir 316 and a supply pump 318, and the first vacuum source is a recirculation pump 320'. The recirculation pump 320' is used to pump print fluid that has passed through the recirculation manifold 104 and the vacuum regulator 212 into the reservoir 316.

[0038] As used herein, a "pump" generally refers to any mechanical or electromechanical device that utilizes pressure or suction to elevate or move fluid through a system. In examples, the recirculation pump 320' can be or include a positive displacement pump, a centrifugal pump, an axial flow pump, or any other pump type.

[0039] As used herein, a "reservoir" is used synonymously with a container and can be any tank, bin, canister, or other receptacle for holding fluid. In examples, the reservoir 316 can include a floor, walls, and / or a lid formed from plastic. In other examples, the floor, walls, and / or lid of the reservoir 316 can be made from metal, or can include metal supports. In examples, the reservoir 316 is used to hold print fluid and can be constructed to be rigid so as to resist expansion and / or contraction of the reservoir due to pressure in the recirculation path 110. In other examples, the reservoir 316 is used to hold print fluid and can be constructed to be flexible so as to allow expansion and / or contraction of the reservoir due to pressure in the recirculation path 110.

[0040] The supply pump 318 is in fluid connection with the reservoir 316 and the supply manifold 102, and is used to pump print fluid from the reservoir 316 to the supply manifold 102. In examples, the supply pump 318 can be or include a positive displacement pump, a centrifugal pump, an axial flow pump, or any other pump type.

[0041] Figure 4 is a block diagram depicting another example of a system for print fluid recirculation. In Figure 4 , components are identified as engines 402. In describing the engines 402, focus is drawn to the specified function of the engines. However, as used herein, the term engine refers generally to the hardware and / or programming to perform the specified function. As shown with respect to Figure 5 , the hardware of an engine may, for example, include one or both of a processor and a memory, while the programming can be code stored on the memory and executable by the processor to perform the specified function.

[0042] In the example of Figure 4 , the print fluid recirculation system 100 is in addition to the system 100 described with respect to Figure 3The described components include, in addition to the control engine 402, an electronic pressure regulator component 404 and a recirculation isolation valve 406. The control engine 402 generally represents a combination of hardware and programming to control the recirculation pump 320'(or any other form of first vacuum source 320( Figure 3 )) and the vacuum regulator 212 to provide a consistent target vacuum pressure to the recirculation manifold 104 as the printing fluid moves through the set of printheads 108. In examples, the control engine 402 can also be used to control operation of the supply pump 318.

[0043] Continuing Figure 4 In examples, the system 100 includes an electronic pressure regulator component 404 in fluid communication with and between the vacuum regulator 212 and the second vacuum source 214. In this example, the electronic pressure regulator component 404 is used to cause a pilot pressure to be provided to the vacuum regulator 212. The pilot pressure is used to cause the vacuum regulator 212 to maintain a recirculation path negative pressure that is proportional to the pilot pressure. In examples, the control engine 402 is used to control the electronic pressure regulator component 404. In this way, the control engine 402 can control the recirculation path negative pressure to maintain a consistent target pressure at the recirculation manifold 104. In some examples, the target pressure can be equal to the pilot pressure. In some other examples, the target pressure can be influenced by changes in the pilot pressure, where the target pressure is less than the pilot pressure. In examples, the electronic pressure regulator component 404 can include a valve, such as a push valve and / or a vent valve, to control the vacuum pressure to a target level. In examples, the electronic pressure regulator component 404 can include an internal pressure sensor to measure the vacuum pressure and programming to adjust the timing of the valve to maintain the target pressure.

[0044] In other examples, the printing fluid recirculation system 100 can include one or more vacuum regulators that include components and programming such that the control engine 402 can directly control the vacuum regulator to maintain a negative pressure in the recirculation path 110 at a consistent target pressure. In such examples, the vacuum regulator can include an internal pressure sensor to measure the vacuum pressure and programming to adjust the timing of the valve to maintain the target pressure. Figure 3 Examples provide such a vacuum regulator 212 with electronic pressure regulator control functionality without a distinct electronic pressure regulator component between the vacuum regulator 212( Figure 3 ) and the second vacuum source 214( Figure 3 ).

[0045] Continuing Figure 4In the example of FIG. 4, the print fluid recirculation path 110 includes a recirculation isolation valve 406 in fluid communication with the recirculation manifold 104. The recirculation isolation valve 406 is used to enable movement of print fluid from the recirculation manifold 104 to the reservoir 316 when the recirculation isolation valve is open. The recirculation isolation valve 406 is used to disable movement of print fluid from the recirculation manifold 104 to the reservoir 316 when the recirculation isolation valve 406 is closed. In examples, the recirculation valve 406 does not hinder or prevent movement of print fluid along the jet operation print fluid return path to the reservoir 316 during a print fluid ejection operation. As used herein, a “print fluid ejection operation” generally refers to an operation at a printer in which print fluid is being ejected from a printhead onto a substrate to form an image, or onto a substrate or maintenance element for servicing the printhead. An example of ejection of fluid from a printhead for servicing purposes is causing the printhead to “spit out” or eject print fluid onto a substrate or maintenance element (e.g., a service station element) to prevent print fluid in the nozzles from drying out. In certain examples, the recirculation path 110 can include a shared path portion that includes a pipe or conduit that is common or identical to a pipe or conduit included in the jet operation print fluid return path (e.g., Figure 9 the shared path portion 110a of FIG. 1.

[0046] In Figure 4 and Figure 5 the above discussion, the control engine 402 is described as a combination of hardware and programming. The control engine 402 can be implemented in a variety of ways. See Figure 5 , the programming can be processor-executable instructions stored on a tangible memory resource 530, and the hardware can include a processing resource 540 to execute the instructions. Thus, the memory resource 530 can be said to store program instructions that, when executed by the processing resource 540, implement the system 100 of Figure 4 and Figure 5 .

[0047] The memory resource 530 generally represents any number of memory components capable of storing instructions executable by the processing resource 540. The memory resource 530 is non-transitory in the sense that it does not include transitory signals but is made up of one or more memory components that store the relevant instructions. The memory resource 530 can be implemented in a single device or distributed across multiple devices. Likewise, the processing resource 540 represents any number of processors capable of executing the instructions stored by the memory resource 530. The processing resource 540 can be integrated in a single device or distributed across multiple devices. Further, the memory resource 530 can be entirely or partially integrated in the same device as the processing resource 540, or it can be separate but accessible by the device and the processing resource 540.

[0048] In one example, the program instructions can be part of an installation package that, when installed, can be executed by the processing resource 540 to implement the system 100. In this case, the memory resource 530 can be a portable medium such as a CD, DVD, or flash drive, or a memory maintained by a server from which the installation package can be downloaded and installed. In another example, the program instructions can be part of one or more applications that are already installed. Here, the memory resource 530 can include integrated memory such as a hard drive, solid state drive, or the like.

[0049] In Figure 5 the executable program instructions stored in the memory resource 530 are depicted as control modules 502. The control modules 502 represent program instructions that, when executed by the processing resource 540, can perform any of the functions described above with respect to the control engine 402 of Figure 4 .

[0050] Figure 6 is a simple schematic diagram illustrating an example of a system for print fluid recirculation. In Figure 6 the example, the print fluid recirculation system 100 includes a supply manifold 102, a recirculation manifold 104, a print bar 106, and a recirculation path 110. The print bar 106 includes a set of inkjet printheads 108 that are in fluid communication with one another, in fluid communication with the supply manifold 102, and in fluid communication with the recirculation manifold 104. In this example, each printhead of the set of printheads 108 is used to eject the same color or other attribute of print fluid.

[0051] The recirculation path 110 is fluidically connected with the supply manifold 102 and the recirculation manifold 104. The recirculation path can include a conduit, a pipe, or a tube, and is used to enable print fluid to be recirculated through the set of printheads 108 at a consistent flow rate. In this example, the recirculation path 110 includes a recirculation isolation valve 406, a vacuum regulator 212 fluidically connected with a first vacuum source that is a recirculation pump 320, a second vacuum source 214, a reservoir 316, and a supply pump 318.

[0052] Continuing Figure 6The recirculation isolation valve 406 is in fluid communication with and between the recirculation manifold 104 and the vacuum regulator 212. The recirculation isolation valve 406 is used to enable movement of print fluid from the recirculation manifold 104 to the vacuum regulator 212 and the reservoir 316 when the recirculation isolation valve is open. The recirculation isolation valve 406 is used to disable movement of print fluid from the recirculation manifold 104 to the vacuum regulator 212 and the reservoir 316 when the recirculation isolation valve 406 is closed. In an example, when the recirculation isolation valve 406 is closed, such that access of print fluid to the vacuum regulator 212 and the reservoir 316 via the print fluid recirculation path 110 is blocked, movement of print fluid between the printheads of the set of printheads 108 and along the jet operation print fluid return path 602 to the reservoir 316 during a print fluid jet operation is not hindered or blocked.

[0053] In this example, the jet operation print fluid return path 602 and the print fluid recirculation path 110 are different or separate paths to the reservoir 316, with no intersection point. In other examples, at least a portion of the recirculation path can be a shared path along a common or same conduit as included in the recirculation path 110 (e.g., a shared path portion 110a of the recirculation path). Figure 9

[0054] The vacuum regulator 212 is in fluid communication with the recirculation manifold 104, the first vacuum source recirculation pump 320', and the second vacuum source 214. The vacuum regulator 212, together with the second vacuum source 214, is used to regulate the negative pressure applied to the recirculation manifold by the recirculation pump 320'. In an example, the vacuum regulator 212 does not allow air or other gas to enter the print fluid recirculation system 100 when the vacuum regulator is used to regulate the vacuum pressure.

[0055] Continuing Figure 6 The recirculation pump 320' is in fluid communication with the reservoir 316 and the vacuum regulator 212, and is used to pump print fluid that has passed through the vacuum regulator 212 into the reservoir 316. The supply pump 318 is in fluid connection with the reservoir 316 and the supply manifold 102, and is used to pump print fluid from the reservoir 316 to the supply manifold 102.

[0056] The control engine 402 generally represents a combination of hardware and programming to control the first vacuum source recirculation pump 320' and the vacuum regulator 212 to provide a controlled and consistent target vacuum pressure as print fluid moves through the set of printheads 108. In this example, the control engine 402 can also control operation of the recirculation pump 320' to effect movement of print fluid into the reservoir 316. In this example, the control engine 402 is also used to control operation of the recirculation isolation valve 406 to enable or disable movement of print fluid from the recirculation manifold 104 to the vacuum regulator 212 and the reservoir 316. Figure 6 ​In examples of the system 100, the recirculation path 110 is such that the printing fluid will be caused to move upward in a portion of the recirculation path 110 against gravity and into the reservoir 316. In examples, such pressure can be between 1.0 psi and 75.0 psi.

[0057] Continuing Figure 6 In this example, the control engine 402 can also control operation of the supply pump 318 to cause the printing fluid to move from the reservoir 316 to the supply manifold 102 at a pressure that is optimal for printing fluid recirculation and that does not damage the printhead 108. In examples, such pressure can be between 1.0 psi and 150.0 psi. In this example, the supply pump 318 is used to cause the printing fluid to move through the printing fluid recirculation path 110 and into the supply manifold 102. In this example, the recirculation path 110 is such that the supply pump 318 is used to cause the printing fluid to move upward through a portion of the recirculation path against gravity and then into the supply manifold 102.

[0058] In examples, the vacuum regulator 212 includes components and programming such that the control engine 402 can directly control the vacuum regulator to maintain a consistent target pressure at the recirculation manifold 104 and thus at the set of printheads 108 that will not damage the printhead 108 or otherwise cause image quality issues when the printhead is to be used for printing fluid ejection operations. In examples, the target pressure at the recirculation manifold can be between -0.1 psi and -10.0 psi. In examples, the target pressure at the set of printheads can be between -0.1 psi and -10.0 psi. In examples, the target negative pressure at the set of printheads can vary according to printhead type and architecture. The vacuum regulator 212 can include an internal pressure sensor to measure the vacuum pressure and programming to regulate the timing of the valve to maintain the target pressure.

[0059] Figure 7 is a simple schematic diagram showing an example of a system for printing fluid recirculation. Figure 7 The example system of Figure 6 The example system of, differs in that the system 100 additionally includes an electronic pressure regulator component 404 that is in fluid communication with and between the vacuum regulator 212 and the second vacuum source 214. In Figure 7 In examples of the system 100, the electronic pressure regulator component 404 is a physically separate and distinct component from the vacuum regulator 212. The electronic pressure regulator component 404, together with the secondary vacuum source 214, causes a pilot pressure to be provided to the vacuum regulator 212. The pilot pressure enables the vacuum regulator 212 to establish a consistent target negative pressure at the recirculation manifold 104 and / or the printhead 108 that is equal to or proportional to the pilot pressure.

[0060] In Figure 7 examples, the control engine 402 is to control the electronic pressure regulator component 404. In this way, the control engine 402 can control the negative pressure (relative to the direction of print fluid flow) within the portion of the recirculation path upstream of the recirculation pump 320' to maintain a consistent target pressure at the recirculation manifold and the print head.

[0061] Figure 8 is a simple schematic diagram illustrating another example of a system for print fluid recirculation. Figure 8 The example system of Figure 7 is similar to the example system of , except that the print fluid recirculation system 100 additionally includes a second supply manifold 102a, a second recirculation manifold 104a, a second print bar 106a, a second recirculation isolation valve 406a, a second vacuum regulator 212a, and a vacuum source 214a. The second print bar 106a includes a second set of inkjet print heads 108a that are in fluid communication with one another, in fluid communication with the second supply manifold 102a, and in fluid communication with the second recirculation manifold 104a. The second supply manifold 102a is fluidically connected with the first supply manifold 102 via a supply manifold bridge 804. In examples, the supply manifold bridge can be or include a conduit, pipe, or tube.

[0062] In this example, the second print bar 106a is positioned on the same print bar support element 802 as the first print bar 106. In this example, the print bar support element 802 has the shape of an arch. In other examples, the print support element can be another vertically curved structure. In other examples, the first and second print heads can be positioned on the support element so as to be horizontally aligned and in the same horizontal alignment. In other examples, the first print bar and the second print bar can be positioned on separate print bar support elements. In this example, each of the first and second sets of print heads 108, 108a are to eject the same color or other attribute of print fluid.

[0063] Continuing with Figure 8The second recirculation isolation valve 406a is in fluid communication with and positioned between the second recirculation manifold 104a and the second vacuum regulator 212a. The second recirculation isolation valve 406a functions to enable movement of print fluid from the second recirculation manifold 104a to the second vacuum regulator 212a and the reservoir 316 when the second recirculation isolation valve 406a is open. The second recirculation isolation valve 406a functions to disable movement of print fluid from the second recirculation manifold 104a to the second vacuum regulator 212a and the reservoir 316 when the second recirculation isolation valve 406a is closed. In an example, when the second recirculation isolation valve 406a is closed and the path of print fluid to the vacuum regulator 212a and the reservoir 316 is blocked in this way, movement of print fluid between the printheads of the second set of printheads 108a and along the jet operation print fluid return path 602 to the reservoir 316 is not blocked or otherwise impeded during a print fluid jet operation.

[0064] The second vacuum regulator 212a is in fluid communication with the second recirculation manifold 104a. The second vacuum regulator 212a, together with the vacuum source 214a, functions to cause a negative pressure to be applied to the second recirculation manifold 104a and in this way cause print fluid to move successively through the second set of printheads 108a, through the second recirculation manifold 104a, and through the second vacuum regulator 212a. In this example, the second vacuum regulator 212a functions to control the vacuum pressure within the system 100 by limiting the flow between the second vacuum source 214a and the second recirculation manifold 104a, thereby precisely controlling the vacuum to a consistent target flow rate.

[0065] The recirculation pump 320' is in fluid communication with the reservoir 316 and the first and second vacuum regulators 212, 212a and functions to pump print fluid that has passed through the first vacuum regulator 212 and / or the second vacuum regulator 212a into the reservoir 316. The supply pump 318 is in fluid connection with the reservoir 316 and the first supply manifold 102 and functions to pump print fluid from the reservoir 316 to the first supply manifold 102.

[0066] The control engine 402 generally represents a combination of hardware and programming to control the first vacuum regulator 212 to apply a negative pressure to the first recirculation manifold 104 to provide a consistent target vacuum pressure as print fluid moves through the first set of printheads 108 and to control the second vacuum regulator 212a to apply a negative pressure to the second recirculation manifold 104a to provide a consistent target vacuum pressure as print fluid moves through the second set of printheads 108a.

[0067] Figure 9 is a simple schematic diagram showing an example of a system for print fluid recirculation. Figure 9 The example system ofFigure 8 The example system differs in that the printing fluid recirculation system 100 additionally includes a first electronic pressure regulator component 404 and a second electronic pressure regulator component 404a, and utilizes a secondary vacuum source 214 to provide vacuum to both the first electronic pressure regulator component 404 and the second electronic pressure regulator component 404a. In this example, the first electronic pressure regulator component 404 is in fluid communication with and located between the first vacuum regulator 212a and the secondary vacuum source 214.

[0068] The first electronic pressure regulator component 404 provides pilot pressure to the first vacuum regulator 212. The pilot pressure provided by the first electronic pressure regulator component 404 causes the first vacuum regulator 212 to maintain a negative pressure proportional to the pilot pressure. The control engine 402 controls the first electronic pressure regulator component 404 to maintain a consistent target pressure at the second recirculation manifold 104 and the second set of printheads 108.

[0069] The second electronic pressure regulator component 404a is in fluid communication with and located between the second vacuum regulator 212a and the secondary vacuum source 214. The second electronic pressure regulator component 404a provides a pilot pressure to the second vacuum regulator 212a. The pilot pressure provided by the second electronic pressure regulator component 404a causes the second vacuum regulator 212a to maintain a negative pressure in the recirculation path proportional to the pilot pressure. The control engine 402 controls the second electronic pressure regulator component 404a to maintain a consistent target pressure at the second recirculation manifold 104a and the second set of printheads 108a.

[0070] exist Figure 9 In this example, the jet-operated print fluid return path 602 includes a shared path portion 110a, wherein the same or common pipes or conduits are also included in the print fluid recirculation path 110. In this example, the pipes of the jet-operated print fluid return path 602 and the print fluid recirculation path 110 intersect at assembly part 604, wherein the shared pipe of the shared path portion 110a supports the movement of print fluid to a reservoir according to both the jet-operated print fluid return path 602 and the print fluid recirculation path 110.

[0071] Figure 10 This is a simplified schematic diagram illustrating an example of a system for printing fluid recirculation. In this example, the first and second printing rods 106, 106a are positioned horizontally and at the same height, rather than as shown below. Figure 7-8The first and second sets of printheads 108, 108a are positioned on an arched or curved support member as in the middle and are used to jet the same color or other attribute of printing fluid. In this example, the recirculation path includes the first and second supply manifolds 102, 102a, the first and second recirculation isolation valves 406, 406a, the vacuum regulator 212, and the recirculation pump 320'. The second supply manifold 102a is fluidically connected with the first supply manifold 102 via the supply manifold bridge 804. The first and second vacuum regulators 102, 102a are fluidically connected with the shared electronic pressure regulator component 404.

[0072] Continuing Figure 10 The first recirculation isolation valve 406 is in fluid communication with and positioned between the first recirculation manifold 104 and the vacuum regulator 212. The first recirculation isolation valve 406 is used to enable movement of printing fluid from the first recirculation manifold 104 to the vacuum regulator 212 when the first recirculation isolation valve 406 is open. The first recirculation isolation valve 406 is used to prevent movement of printing fluid from the first recirculation manifold 104 to the vacuum regulator 212 when the first recirculation isolation valve 406 is closed. In the example, when the first recirculation isolation valve 406 is closed and the passageway of printing fluid into the vacuum regulator 112 and the recirculation path 110 is blocked, movement of printing fluid along the jet operation printing fluid return path 602 to the reservoir 316 is not blocked during a printing fluid jet operation.

[0073] The vacuum regulator 212 is in fluid communication with the first recirculation manifold 104. The vacuum regulator 212, together with the secondary vacuum source 214, is used to cause a negative pressure to be applied to the first recirculation manifold 104 and in this way cause printing fluid to move successively through the first set of printheads 108a, through the first recirculation manifold 104, and through the vacuum regulator 212. In this example, the vacuum regulator 212 regulates the vacuum pressure applied to the first and second sets of printheads 108, 108a by limiting the flow between the secondary vacuum source 214 and the first recirculation manifold 104, thereby precisely controlling the vacuum to a consistent target flow rate.

[0074] Continuing Figure 10The second recirculation isolation valve 406a is in fluid communication with and positioned between the second recirculation manifold 104a and the vacuum regulator 212. When the second recirculation isolation valve 406a is open, it allows printing fluid to move from the second recirculation manifold 104a to the vacuum regulator 212. When the second recirculation isolation valve 406a is closed, it prevents printing fluid from moving from the second recirculation manifold 104a to the vacuum regulator 212. In this example, when the second recirculation isolation valve 406a is closed and the passage of printing fluid via the vacuum regulator to the recirculation path 110 is blocked, during the printing fluid ejection operation, the movement of printing fluid between the printheads of the set of printheads 108 and along the ejection operation printing fluid return path 602 to the reservoir 316 is not obstructed or otherwise impeded.

[0075] Vacuum regulator 212 is in fluid communication with the second recirculation manifold 104a. Vacuum regulator 212, together with secondary vacuum source 214, is used to cause a negative pressure to be applied to the second recirculation manifold 104a, and to cause printing fluid to move sequentially through a set of second printheads 108a, through the second recirculation manifold 104a, and through vacuum regulator 212. In this example, vacuum regulator 212 controls the vacuum pressure within system 100 by limiting the flow rate between vacuum source 214 and the second recirculation manifold 104a, and in this way precisely controls the vacuum to a consistent target flow rate.

[0076] exist Figure 10 In the example, when the first and second print heads 106, 106a are positioned in a horizontal orientation and at the same height relative to the floor, a single vacuum regulator 212 can be used to influence the negative pressure applied to the first and second sets of print heads 108, 108a. Figure 10 In the example, the negative pressure to be applied to the first recirculation manifold 104 and the negative pressure to be applied to the second recirculation manifold 104a can be the same pressure, ranging from -0.1 psi to -10.0 psi. Since the vertical distance between the first print bar 106 and the first vacuum regulator 212 is the same as the vertical distance between the second print bar 106a and the second vacuum regulator 212, different pressures are not required.

[0077] On the contrary, Figure 8 In the example, the first and second printing rods 106, 106a are located at different heights, and each of the first and second printing rods has a dedicated vacuum regulator to achieve different negative pressures and thus compensate for the height difference of the printing rods. Figure 8In the example, since the effect of gravity assist on the printing fluid returning from the first print bar 106 to the recirculation pump 320' is greater than the effect of gravity assist on the second print bar 106a, the negative pressure to be applied to the first recirculation manifold 104 (e.g., -1.0 psi to -2.0 psi) can be less than the negative pressure to be applied to the second recirculation manifold 104a (e.g., -1.5 psi to -2.5 psi).

[0078] The recirculation pump 320' is in fluid communication with the reservoir 316 and the vacuum regulator 212, and is used to pump printing fluid that has passed through the vacuum regulator 212 into the reservoir 316. The supply pump 318 is in fluid communication with the reservoir 316 and the first supply manifold 102, and is used to pump printing fluid from the reservoir 316 into the first supply manifold 102.

[0079] In this example, control engine 402 typically represents a combination of hardware and programming to control vacuum regulator 212 to apply negative pressure to the first recirculation manifold 104 to provide a consistent target vacuum pressure as print fluid moves through the first set of printheads 108, and to apply the same or proportional negative pressure to the second recirculation manifold 104a to provide a consistent target vacuum pressure as print fluid moves through the second set of printheads 108a.

[0080] Figure 11 This is a bottom view of an example of a first printing rod, a first supply manifold, a first recirculation manifold, a second printing rod, a second supply manifold, and a second recirculation manifold. Figure 12A supply Figure 11 A perspective view of an example of the first supply manifold shown. Figure 12B supply Figure 11 A perspective view of an example of a second supply manifold shown. Figure 12C supply Figure 11 A perspective view of an example of the first recirculation manifold shown. Figure 12D supply Figure 11 A perspective view of an example of a second recirculation manifold shown.

[0081] refer to Figure 12A and Figure 12C Let's take a look Figure 11The first print head 106 includes a first set of print heads 108, which are in fluid communication with each other via conduit 1112, to a first supply manifold 102, and to a first recirculation manifold 104. In this example, the first supply manifold 102 includes a chamber 1202 branching into or connected to a plurality of dispensing openings 1102, through which printing fluid will be dispensed to the first set of print heads 108 via the connecting conduit 1112. The first supply manifold is used to receive printing fluid via an inlet opening 1108 connected to a recirculation path 110. In this example, the printing fluid may be supplied via a supply pump (e.g., such as a pump included in the recirculation path). Figure 6 , Figure 7 , Figure 8 , Figure 9 or Figure 10 The supply pump 318 is pushed to the front supply manifold 102. In the example, the first supply manifold 102 may include a valve for controlling the movement of printing fluid through the first supply manifold or an interface to an electronic network.

[0082] The first print bar 106 holds a first set of printheads 108. In this example, each printhead 108 ejects a printing fluid of the same color or other properties. In this example, the depicted side of the first print bar 106 is used to face the substrate during the printing fluid ejection operation and holds seven printheads 108, wherein each printhead houses five printhead dies. An example printhead die of the first print bar 106 is assigned reference numeral 1106. In this example, each printhead die holds a set of printhead nozzles for ejecting printing fluid onto the substrate (the printhead nozzles are located in...). Figure 11 (Not visible in the image). In other examples, print head 106 may include any number of printheads, wherein each printhead includes any number of dies, and each die includes any number of printhead nozzles. In the example, the first supply manifold 102 may include a valve for controlling the movement of printing fluid through the first supply manifold or an interface to an electronic network.

[0083] Continue to refer to Figure 12A and Figure 12C Let's take a look Figure 11 The first recirculation manifold 104 includes a chamber 1204 branching into or connected to a plurality of collection openings 1104 through which printing fluid is received from the first set of printheads 108 via conduit 1112. The first recirculation manifold 104 includes a delivery opening 1110 through which printing fluid is moved via a connected conduit to a recirculation path 110.

[0084] refer to Figure 12B and Figure 12D Let's take a look Figure 11A second supply manifold 102a is connected to a second print bar 106a and is used to receive printing fluid via an inlet opening 1122, which is connected to a first supply manifold 102 via a conduit of a supply manifold bridge 804. In this example, the second supply manifold 102a includes a chamber 1202a branching into or connected to a dispensing opening 1102a, through which printing fluid is dispensed to a second set of printheads 108a via a connecting conduit 1112. The second print bar 106a holds the second set of printheads 108a. In this example, each printhead 108a is used to eject printing fluid of the same color or other properties as that ejected by the first set of printheads 108. In this example, the depicted side of the second print bar 106a is used to face the substrate during printing fluid ejection operation and holds seven printheads, each of which houses five printhead dies. An example printhead die of the second print bar 106a is assigned reference numeral 1106a. In this example, each printhead die holds a set of printhead nozzles for spraying printing fluid onto the substrate.

[0085] Continue to refer to Figure 12B and Figure 12D Let's take a look Figure 11 The second recirculation manifold 104a includes a chamber 1204a branching into or connected to a plurality of collection openings 1104a through which printing fluid is received from the second set of printheads 108a via conduit 1112. The second recirculation manifold 104a includes a delivery opening 1110a through which printing fluid is moved via a connected conduit to a recirculation path 110. In the example, the second supply manifold 102a may include a valve for controlling the movement of printing fluid through the second supply manifold or an interface to an electronic network.

[0086] Figure 13 This is a bottom view of another example of a first printing manifold, a first supply manifold, a first recirculation manifold, a second printing manifold, a second supply manifold, and a second recirculation manifold. In this example, the first supply manifold 102 and the first recirculation manifold 104 are positioned adjacent to the long side of the rectangular first printing manifold 106 (instead of as shown in...). Figure 11 In the example, the second supply manifold 102a and the second recirculation manifold 104a are positioned adjacent to the long side of the rectangular second printing rod 106a (instead of as in the example). Figure 11 (As in the example, adjacent to the end of the rectangular second printing bar 106a). In other respects, the first and second printing bars 106, 106a, the first and second supply manifolds 102, 102a, and the first and second recirculation manifolds 104, 104a function substantially similarly. Figure 11The system 100 described herein is an example of its functionality.

[0087] Figure 14 This is a flowchart illustrating the implementation of a method for printing fluid recirculation. (In the discussion...) Figure 14 You can refer to this when... Figure 1-13 The components described herein. Such references are made to provide examples of context, not to limit what can be achieved. Figure 14 The method described involves the controlled application of negative pressure to the recirculation manifold, causing print fluid to move sequentially through the supply manifold, a set of printheads, the recirculation manifold, and the recirculation path (box 1402). Return to reference. Figure 4-10 Control engine 402 ( Figure 4 and Figure 6-10 ) or control module 502 ( Figure 5 When executed by processing resource 540, it can be responsible for implementing block 1402.

[0088] Figure 15 This is a flowchart of another implementation of a method for printing fluid recirculation. (In the discussion...) Figure 15 You can refer to this when... Figure 1-13 The components described herein. Such references are made to provide examples of context, not to limit what can be achieved. Figure 15 The way or manner of description.

[0089] Such as about Figure 14 As described, a controlled application of negative pressure to the recirculation manifold causes printing fluid to move sequentially through the supply manifold, a set of printheads, the recirculation manifold, and the recirculation path (box 1402).

[0090] The position of the recirculation isolation valve, included within the recirculation path, is controlled to be either open or closed. When the recirculation valve is open, the movement of print fluid along the recirculation path is unimpeded. When the recirculation isolation valve is closed, the movement of print fluid along the recirculation path is impeded, but the movement of print fluid along the print fluid return path during the print fluid ejection operation is unimpeded (box 1504). Return to Reference Figure 4-10 Control engine 402 ( Figure 4 and Figure 6-10 ) or control module 502 ( Figure 5 When executed by processing resource 540, it can be responsible for implementing block 1504.

[0091] Figure 1-15 It helps to depict the architecture, functionality, and operation of various examples. In particular, Figure 1-13Various physical and logical blocks are described. Various blocks are defined at least in part as programs or program designs. Each such block, portion thereof, or various combinations thereof can represent modules, segments, or portions of codes that include executable instructions for implementing any specified logical function(s). Each block or various combinations thereof can represent a circuit or multiple interconnected circuits for implementing the specified logical function(s). Examples can be implemented in a memory resource used by or in conjunction with a processing resource. A "processing resource" refers to an instruction execution system such as a computer / processor-based system or an ASIC (application specific integrated circuit) or other system that can fetch or obtain instructions and data from computer-readable media and execute the instructions contained therein. A "memory resource" is a non-transitory storage medium that can contain, store, or maintain programs and data used by or in conjunction with the instruction execution system. The term "non-transitory" is used only to clarify that the term media as used herein does not encompass a signal. Thus, the memory resource can include physical media such as electronic, magnetic, optical, electromagnetic, or semiconductor media. More specific examples of suitable computer-readable media include, but are not limited to, hard drives, solid state drives, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), flash drives, and portable compact discs.

[0092] Although Figure 14 and Figure 15 the flowcharts illustrate a particular order of execution, the order of execution can be different from that which is described. For example, two or more blocks or arrows can be executed concurrently or in a different order than that which is depicted. Also, a block or arrow that is, e.g., depicted below another block or arrow can indicate a dependency of the block or arrow on the other block or arrow. For example, block A can be executed before block B or concurrently with block B. In another example, block B can be executed before block A or concurrently with block A. In another example, block A and block B can be executed concurrently. These variations are within the scope of the present disclosure.

[0093] It should be appreciated that the previous description of the disclosed examples is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these examples will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other examples without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the examples shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. All features disclosed in the specification (including any accompanying claims, abstract, and drawings) and any methods or processes disclosed herein can be combined in any combination, provided that the features, blocks, or stages are not mutually inconsistent, as will be apparent to one of ordinary skill in the art. The use herein of "first," "second," "third," etc. to describe various elements is only to distinguish one element from another, and is not a requirement as to the sequence or order of these elements, unless otherwise specified.

Claims

1. A printing fluid recirculation system, comprising: a first supply manifold; a first recirculation manifold; a first printbar comprising a first plurality of printheads in fluid communication with one another, in fluid communication with the first supply manifold, and in fluid communication with the first recirculation manifold; a second supply manifold; a second recirculation manifold; a second printbar comprising a second plurality of printheads in fluid communication with one another, in fluid communication with the second supply manifold, and in fluid communication with the second recirculation manifold; a supply manifold bridge enabling printing fluid to be in fluid communication between the first supply manifold and the second supply manifold; and a recirculation path in fluid connection with the first supply manifold, the first recirculation manifold, the second supply manifold, and the second recirculation manifold, the recirculation path enabling printing fluid to be recirculated through the first plurality of printheads and the second plurality of printheads at a controlled flow rate. the recirculation path comprises 2. The system of claim 1, wherein, a first vacuum source in fluid communication with the first recirculation manifold, wherein the first vacuum source is to cause a negative pressure to be applied to the first recirculation manifold; and a vacuum regulator in fluid communication with the first recirculation manifold, the first vacuum source, and a second vacuum source, wherein the vacuum regulator is to regulate, in conjunction with the second vacuum source, the negative pressure applied to the first recirculation manifold by the first vacuum source.

3. The system of claim 2, further comprising a reservoir; and the first vacuum source is a recirculation pump and is to pump printing fluid that has passed through the first recirculation manifold and the vacuum regulator into the reservoir. wherein 4. The system of claim 2, further comprising an electronic pressure regulator component in fluid communication with and between the vacuum regulator and the second vacuum source, the electronic pressure regulator component to cause a pilot pressure to be provided to the vacuum regulator.

5. The system of claim 2, further comprising a control engine to control the first vacuum source and the vacuum regulator to provide a target vacuum pressure as printing fluid moves through the first plurality of printheads.

6. The system of claim 2, the recirculation path comprises a recirculation isolation valve and a reservoir in fluid communication with the first recirculation manifold; and wherein wherein the recirculation isolation valve is to enable printing fluid to move from the first recirculation manifold to the reservoir when the recirculation isolation valve is open and is to not enable printing fluid to move from the first recirculation manifold to the reservoir when the recirculation isolation valve is closed. movement of printing fluid along an ejection operation printing fluid return path during a printing fluid ejection operation is not impeded when the recirculation isolation valve is closed.

7. The system of claim 6, wherein, ​ 8. The system of claim 7, wherein, The recirculation path includes a shared path portion that includes a pipe that is common or identical to a pipe included in the jet operation printing fluid return path.

9. The system of claim 2, wherein, The recirculation path includes a reservoir and a supply pump in fluid connection with the reservoir; wherein the first vacuum source is a recirculation pump for pumping printing fluid that has passed through the first recirculation manifold into the reservoir; and wherein the supply pump is for pumping printing fluid from the reservoir to a supply manifold.

10. The system of claim 1, wherein The recirculation path includes a recirculation pump, a vacuum regulator, and a vacuum source for causing negative pressure to be applied to the first recirculation manifold to cause printing fluid to move sequentially through the first plurality of printheads and the first recirculation manifold, and for causing negative pressure to be applied to the second recirculation manifold to cause printing fluid to move sequentially through the second plurality of printheads and the second recirculation manifold.

11. A printing fluid recirculation method, comprising: controlling application of a target negative pressure to a first recirculation manifold and a second recirculation manifold, thereby causing printing fluid to move sequentially through a first supply manifold, a first printbar comprising a first plurality of printheads in fluid communication with one another, the first recirculation manifold, a recirculation path, a second supply manifold, the second recirculation manifold, a second printbar comprising a second plurality of printheads in fluid communication with one another, in fluid communication with the second supply manifold, and in fluid communication with the second recirculation manifold, wherein a supply manifold bridge enables printing fluid to fluidly communicate between the first supply manifold and the second supply manifold, wherein the recirculation path is in fluid connection with the first supply manifold, the second supply manifold, the first recirculation manifold, and the second recirculation manifold, and wherein the recirculation path enables printing fluid to be recirculated through the first plurality of printheads and the second plurality of printheads at a controlled flow rate.

12. The method of claim 11, further comprising: controlling a position of a recirculation isolation valve included in the recirculation path to an open position and a closed position, wherein when the recirculation isolation valve is in the open position, movement of printing fluid along the recirculation path is not impeded; and wherein when the recirculation isolation valve is in the closed position, movement of printing fluid along the recirculation path is impeded, and movement of printing fluid along a jet operation printing fluid return path during a printing fluid jetting operation is not impeded.

13. A printing fluid recirculation system, comprising: a first supply manifold; a first recirculation manifold; a first plurality of printheads in fluid communication with one another, in fluid communication with the first supply manifold, and in fluid communication with the first recirculation manifold; a second supply manifold; a second recirculation manifold; a second plurality of printheads in fluid communication with one another, in fluid communication with the second supply manifold, and in fluid communication with the second recirculation manifold; a supply manifold bridge fluidly connecting the first supply manifold and the second supply manifold; a recirculation path fluidically connected with the first and second supply manifolds and fluidically connected to the first and second recirculation manifolds, the recirculation path including a reservoir and at least one vacuum source; and a control engine to direct the at least one vacuum source to control application of negative pressure to the first and second recirculation manifolds and thereby enable recirculation of printing fluid through the first and second pluralities of printheads at a controlled flow rate.

14. The system of claim 13, wherein the recirculation path including a first recirculation isolation valve in fluid communication with the first recirculation manifold and a second recirculation isolation valve in fluid communication with the second recirculation manifold; wherein the first recirculation isolation valve is to enable movement of printing fluid from the first recirculation manifold to the reservoir when the first recirculation isolation valve is open and to disable movement of printing fluid from the first recirculation manifold to the reservoir when the first recirculation isolation valve is closed; and wherein the second recirculation isolation valve is to enable movement of printing fluid from the second recirculation manifold to the reservoir when the second recirculation isolation valve is open and to disable movement of printing fluid from the second recirculation manifold to the reservoir when the second recirculation isolation valve is closed.

Images