Jetting module install mechanism

A printer includes a plurality of jetting modules each including a first alignment feature, a plurality of nozzles through which fluid may be jetted and fluid and electrical connections; a printhead frame having a plurality of jetting-module receiving receptacles each of which receives one of the jetting modules, each receiving receptacle having a second alignment feature corresponding to the first alignment feature of a jetting module: a jetting module installation device having a pocket for receiving a jetting module, wherein the jetting module installation device includes a latch mechanism that, in a first position, is latched to the printhead frame securing the jetting module in a jetting module receiving receptacle with the first alignment feature engaging a corresponding second alignment feature of the printhead frame; the latch mechanism that, in a second position, is unlatched from the printhead frame so that the jetting module is not secured in the jetting module receiving receptacle; and wherein the jetting module installation device includes a coupling frame having fluid and electrical connections that correspond to the fluid and electrical connections of the jetting module, and the installation device includes a mechanism move the coupling frame relative to the jetting module to cause the fluid and electrical connections of the coupling frame to mate to the fluid and electrical connections of the jetting module.

FIELD OF THE INVENTION

This invention relates generally to the field of digitally controlled printing devices, such as continuous ink jet printers. More specifically, the invention relates to a method for installing and properly aligning field-replaceable jetting modules in which the jetting modules are spaced densely within the ink jet printer.

BACKGROUND OF THE INVENTION

Traditionally, digitally controlled color printing capability is accomplished by one of two technologies. Both require independent ink supplies for each of the colors of ink provided. Ink is fed through channels formed in the printhead. Each channel includes a nozzle from which droplets of ink are selectively extruded and deposited upon a medium. Typically, each technology requires separate ink delivery systems for each ink color used in printing. Ordinarily, the three primary subtractive colors, i.e. cyan, yellow and magenta, are used because these colors can produce, in general, up to several million shades or color combinations.

The first technology, commonly referred to as “drop on demand” ink jet printing, selectively provides ink droplets for impact upon a recording surface using a pressurization actuator (thermal, piezoelectric, etc.). Selective activation of the actuator causes the formation and ejection of a flying ink droplet that crosses the space between the printhead and the print media and strikes the print media. The formation of printed images is achieved by controlling the individual formation of ink droplets, as is required to create the desired image. Typically, a slight negative pressure within each channel keeps the ink from inadvertently escaping through the nozzle, and also forms a slightly concave meniscus at the nozzle helping to keep the nozzle clean.

Conventional, droplet-on-demand ink jet printers utilize a heat actuator or a piezoelectric actuator to produce the ink jet droplet at orifices of a print head. With heat actuators, a heater, placed at a convenient location, heats the ink to cause a localized quantity of ink to phase change into a gaseous steam bubble that raises the internal ink pressure sufficiently for an ink droplet to he expelled. With piezoelectric actuators, a mechanical force causes an ink droplet to he expelled.

The second technology, commonly referred to as “continuous stream” or simply “continuous” ink jet printing, uses a pressurized ink source that produces a continuous stream of ink droplets. Traditionally. the ink droplets are selectively electrically charged. Deflection electrodes direct those droplets that have been charged along a flight path different from the flight path of the droplets that have not been charged. Either the deflected or the non-deflected droplets can he used to print on receiver media while the other droplets go to an ink capturing mechanism (catcher, interceptor, gutter, etc.) to be recycled or disposed. U.S. Pat. No. 1,941,001, issued to Hansell, on Dec. 26, 1933, and U.S. Pat. No. 3,373,437 issued to Sweet et al., on Mar. 12, 1968, each disclose an array of continuous ink jet nozzles wherein ink droplets to be printed arc selectively charged and deflected towards the recording medium.

Continuous ink jet printing systems use jetting modules to eject the droplet toward the print media. These units contain the electrical and fluid connections necessary for the jetting module to properly function. As can he expected, occasionally the jetting modules may need replacing due to normal wear and tear.

Commonly assigned U.S. patent application 2009/0295878 discloses a continuous inkjet printing system having a method and apparatus for replacing jetting modules. This disclosure is more than sufficient for some ink jet printers: however, in continuous ink jet printers having the jetting modules densely populated, additional complexities arise. For example, proper alignment of the print head to the deflection mechanism is even more technically demanding. Without belaboring each additional complexity, and as may be expected, it is sufficient to note that proper alignment of other components may also be more demanding.

Although the above described system is satisfactory, improvements in installing jetting modules for overcoming the above shortcomings are always desirable.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the invention, the invention resides in a printer comprising (a) a plurality of jetting modules each including a first alignment feature, a plurality of nozzles through which fluid may be jetted and fluid and electrical connections; (b) a printhead frame having a plurality of jetting-module receiving receptacles each of which receives one of the jetting modules, each receiving receptacle having a second alignment feature corresponding to the first alignment feature of a jetting module: (c) a jetting module installation device having a pocket for receiving a jetting module, wherein the jetting module installation device includes a latch mechanism that, in a first position, is latched to the printhead frame securing the jetting module in a jetting module receiving receptacle with the first alignment feature engaging a corresponding second alignment feature of the printhead frame; (d) the latch mechanism that, in a second position, is unlatched from the printhead frame so that the jetting module is not secured in the jetting module receiving receptacle; and wherein the jetting module installation device includes a coupling frame having fluid and electrical connections that correspond to the fluid and electrical connections of the jetting module, and the installation device includes a mechanism move the coupling frame relative to the jetting module to cause the fluid and electrical connections of the coupling frame to mate to the fluid and electrical connections of the jetting module.

DETAILED DESCRIPTION OF THE INVENTION

The present description will he directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. In the following description and drawings, identical reference numerals have been used, where possible, to designate identical elements.

The example embodiments of the present invention are illustrated schematically and not to scale for the sake of clarity. One of the ordinary skills in the art will he able to readily determine the specific size and interconnections of the elements of the example embodiments of the present invention.

As described herein, the example embodiments of the present invention provide a printhead or printhead components typically used in inkjet printing systems. However, many other applications are emerging which use inkjet printheads to emit liquids (other than inks) that need to be finely metered and deposited with high spatial precision. As such, as described herein, the terms “liquid” and “ink” refer to any material that can be ejected by the printhead or printhead components described below.

Referring toFIG. 1, a continuous ink jet printer system20includes an image source22such as a scanner or computer which provides raster image data, outline image data in the form of a page description language, or other forms of digital image data. This image data is converted to half-toned bitmap image data by an image processing unit24which also stores the image data in memory. A plurality of drop forming mechanism control circuits26read data from the image memory and applies time-varying electrical pulses to a drop forming mechanism(s)28that are associated with one or more nozzles of a printhead30. These pulses are applied at an appropriate time, and to the appropriate nozzle, so that drops formed from a continuous ink jet stream will form spots on a recording medium32in the appropriate position designated by the data in the image memory.

Recording medium32is moved relative to printhead30by a recording medium transport system34, which is electronically controlled by a recording medium transport control system36, and which in turn is controlled by a micro-controller38. The recording medium transport system shown inFIG. 1is a schematic only, and many different mechanical configurations are possible. For example, a transfer roller could be used as recording medium transport system34to facilitate transfer of the ink drops to recording medium32. Such transfer roller technology is well known in the art. In the case of page width printheads, it is most convenient to move recording medium32past a stationary printhead. However in the case of scanning print systems, it is usually most convenient to move the printhead along one axis (the sub-scanning direction) and the recording medium along an orthogonal axis (the main scanning direction) in a relative raster motion.

Ink is contained in an ink reservoir40under pressure. In the non-printing state, continuous ink jet drop streams are unable to reach recording medium32due to an ink catcher42that blocks the stream and which may allow a portion of the ink to be recycled by an ink recycling unit44. The ink recycling unit reconditions the ink and feeds it back to reservoir40. Such ink recycling units are well known in the art. The ink pressure suitable for optimal operation will depend on a number of factors, including geometry and thermal properties of the nozzles and thermal properties of the ink. A constant ink pressure can be achieved by applying pressure to ink reservoir40under the control of ink pressure regulator46.

The ink is distributed to printhead30through an ink channel47. The ink preferably flows through slots or holes etched through a silicon substrate of printhead30to its front surface, where a plurality of nozzles and drop forming mechanisms, for example, heaters, are situated. When printhead30is fabricated from silicon, drop forming mechanism control circuits26can be integrated with the printhead. Printhead30also includes a deflection mechanism (not shown inFIG. 1) which is described in more detail below with reference toFIGS. 2 and 3.

Referring toFIG. 2, a schematic view of a continuous liquid printhead30is shown. A jetting module48of printhead30includes an array or a plurality of nozzles50formed in a nozzle plate49. InFIG. 2, nozzle plate49is affixed to jetting module48. However, if preferred, nozzle plate49can be integrally formed with jetting module48.

Liquid, for example, ink, is emitted under pressure through each nozzle50of the array to form filaments of liquid52. InFIG. 2, the array or plurality of nozzles extends into and out of the figure and preferably the nozzle array is a linear array of nozzles.

Jetting module48is operable to form liquid drops having a first size and liquid drops having a second size through each nozzle. To accomplish this, jetting module48includes a drop stimulation or drop forming device or transducer28, for example, a heater. piezoelectric transducer, EHD transducer and a MEMS actuator, that, when selectively activated perturbs each filament of liquid52, for example, ink, to induce portions of each filament to break off from the filament and coalesce to form drops54,56.

Typically, one drop forming device28is associated with each nozzle50of the nozzle array. However, a drop forming device28can he associated with groups of nozzles50or all of nozzles50of the nozzle array.

When printhead30is in operation, drops54,56are typically created in a plurality of sizes, for example, in the form of large drops56, a first size, and small drops54, a second size. The ratio of the mass of the large drops56to the mass of the small drops54is typically approximately an integer between 2 and 10. A drop stream58including drops54,56follows a drop path or trajectory57.

Printhead30also includes a gas flow deflection mechanism60that directs a flow of gas62, for example, air, past a portion of the drop trajectory57. This portion of the drop trajectory is called the deflection zone64. As the flow of gas62interacts with drops54,56in deflection zone64it alters the drop trajectories. As the drop trajectories pass out of the deflection zone64they are traveling at an angle, called a deflection angle, relative to the un-deflected drop trajectory57.

Small drops54are more affected by the flow of gas than are large drops56so that the small drop trajectory66diverges from the large drop trajectory68. That is, the deflection angle for small drops54is larger than for large drops56. The flow of gas62provides sufficient drop deflection and therefore sufficient divergence of the small and large drop trajectories so that catcher42(shown inFIG. 1) can be positioned to intercept the small drop trajectory66so that drops following this trajectory arc collected by catcher42while drops following the other trajectory bypass the catcher and impinge a recording medium32(shown inFIG. 1).

When catcher42is positioned to intercept small drop trajectory66, large drops56are deflected by a sufficient amount to avoid contact with catcher42and allowing the large drops56to strike the print media. When catcher42is positioned to intercept small drop trajectory66, large drops56are the drops that print, and this is referred to as large drop print mode.

Jetting module48includes an array or a plurality of nozzles50. Liquid, for example, ink, supplied through channel47, is emitted under pressure through each nozzle50of the array to form filaments of liquid52. InFIG. 2, the array or plurality of nozzles50extends into and out of the figure.

Drop stimulation or drop forming device28(shown inFIGS. 1 and 2) associated with jetting module48is selectively actuated to perturb the filament of liquid52to induce portions or the filament to break off from the filament to form drops. In this way, drops are selectively created in the form of large drops and small drops that travel toward a recording medium32.

Referring toFIGS. 2 and 3, positive pressure gas flow structure61of gas flow deflection mechanism60is located on a first side of drop trajectory57. Positive pressure gas flow structure61includes first gas flow duct72that includes a lower wall74and an upper wall76. Gas flow duct72directs gas flow62supplied from a positive pressure source92at downward angle θ of approximately a 45° relative to liquid filament52toward drop deflection zone64(also shown inFIG. 2). An optional seal(s)80provides an air seal between jetting module48and upper wall76of gas flow duct72.

Upper wall76of gas flow duct72does not need to extend to drop deflection zone64(as shown inFIG. 3). InFIG. 3, upper wall76ends at a wall96of jetting module48. Wall96of jetting module48serves as a portion of upper wall76ending at drop deflection zone64.

Negative pressure gas flow structure63of gas flow deflection mechanism60is located on a second side of drop trajectory57. Negative pressure gas flow structure includes a second gas flow duct78located between catcher42and an upper wall82that exhausts gas flow from deflection zone64. Second duct78is connected to a negative pressure source94that is used to help remove gas flowing through second duct78. An optional seal(s)80provides an air seal between jetting module48and upper wall82. As shown inFIG. 3, gas flow deflection mechanism60includes positive pressure source92and negative pressure source94. However, depending on the specific application contemplated, gas flow deflection mechanism60can include only one of positive pressure source92and negative pressure source94.

Gas supplied by first gas flow duct72is directed into the drop deflection zone64, where it causes large drops56to follow large drop trajectory68and small drops54to follow small drop trajectory66. As shown inFIG. 3, small drop trajectory66is intercepted by a front face90of catcher42. Small drops54contact face90and flow down face90and into a liquid return duct86located or formed between catcher42and a plate88. Collected liquid is either recycled and returned to ink reservoir40(shown inFIG. 1) for reuse or discarded. Large drops56bypass catcher42and travel on to recording medium32. Alternatively, catcher42can be positioned to intercept large drop trajectory68while not intercepting the small drop trajectory66. Large drops56contact catcher42and flow into a liquid return duct located or formed in catcher42. Collected liquid is either recycled for reuse or discarded. Small drops54bypass catcher42and travel on to recording medium32.

Referring toFIG. 2, alternatively, deflection can he accomplished by applying heat asymmetrically to filament of liquid52using an asymmetric heater51. When used in this capacity, asymmetric heater51typically operates as the drop forming mechanism in addition to the deflection mechanism. This type of drop formation and deflection is known having been described in, for example, U.S. Pat. No. 6,079,821, issued to Chwalek et al. on Jun. 27, 2000.

As shown inFIG. 3, catcher42is a type of catcher commonly referred to as a “Coanda” catcher. However, the “knife edge” catcher shown inFIG. 1and the “Coanda” catcher shown inFIG. 3are interchangeable and work equally well. Alternatively, catcher42can be of any suitable design including, but not limited to, a porous face catcher, a delimited edge catcher, or combinations of any of those described above.

Referring toFIG. 4, there is shown a perspective view of a portion of a continuous printer illustrating the jetting module48in its uninstalled position for clarity in understanding the present invention. The printer100includes a module removing device110that includes a lift plate115and four post members118for supporting the lift plate. The lift plate has a plurality of openings125in which an install device130is positioned. Although only one install device is shown inFIG. 4, each opening can receive an install device. The openings125are shown as rectangular shaped openings, but the opening need not be limited to rectangular shaped openings. Any opening shape suitable for receiving the install devices may be used. It facilitates understanding to note that the module removing device includes other well known components in order to be operational as will he readily recognized by those skilled in the art from this description. For example, one or more motors120are needed for moving the lift plate upwardly and downwardly.

Each install device includes a pocket135for receiving the jetting module48. The pocket135is seen most clearly inFIG. 10, where the jetting module48is shown centered in the pocket135. The install device130preferably includes detents140that engage features142on the jetting module48to center the jetting module48within the pocket135. The install device also includes a latch mechanism144comprised of two latch devices as will be described more fully later herein.

Returning toFIG. 4, a printhead frame146of the printhead30supports the four posts118of the module removing device118and includes a plurality of jetting-module receiving receptacles147each aligned with a corresponding opening125of the lift plate115. The printhead frame146also includes two upwardly extending mating portions148positioned on opposite ends of each receiving receptacles147, although only one pair is shown for drawing clarity. The mating portions148matingly receive the install device130and each includes a post150so that the install device aligns properly as it is lowered onto the printhead frame146, as will be discussed more fully later herein.

Referring toFIG. 5, there is shown a front view of the jetting module48installed within an install device130. The install device130is located in one of the openings125of the lift plate115of the module removing device110module removing device and is secured to the lift plate115of the module removing device110by the latch mechanism144. The latch mechanisms144cause a first latch device152of the latch mechanism144to extend out the sides of the install device130. The first latch device152is trapped in catch154of the lift plate115. This ensures the stability of the install device130as the lift plate115of the module removing device110is lowered downwardly.

As the lift plate115of the module removing device110is lowered, the posts150of the upwardly extending mating portions148engage the install device130. The first latch device152that secures the install device130to the lift plate115allows the install device130to shift around within the rectangular shaped opening125so that the install device130may be guided by the posts150as it is lowered. As a result of lowering the install device130, the jetting module48, located in the pocket135of the install device130, is correspondingly lowered into its installed position as shown inFIG. 6.

Referring toFIGS. 5 and 6, since the jetting module48has been centered, in the pocket135of the install device130by the detents140, and the install device130has been guided by the posts150as it was lowered, the jetting module43is located appropriately so that the first alignment features156of the jetting module48will properly engage the second alignment features158of the printhead frame146. The detents140that locate the jetting module48in the pocket135provide sufficient compliance so that the jetting module position will he determined by the engagement of the first and second alignment features156and158rather than by the detent mechanism of the install device130.

Referring toFIG. 6, there is shown the lift plate115of the module removing device110after it has been lowered downwardly onto the printhead frame146so that the two mating portions148are mated to the install device130. The latch mechanisms144are then moved which cause the first latch device152to retract from the catch154. This unlatches the install device130from the lift plate115of the module removal device110. Concurrently, the latch mechanism144causes a second latch device160to secure the install device130to the printhead frame146by engaging the mating portions148.

Referring toFIG. 7, after the jetting module48has been properly positioned in the jetting module receiving receptacle147, the coupling frame portion162of the install device130is employed to make fluid and electric connections to the jetting module48. A compliant coupling mechanism164, shown here as a spring, is used to mount the coupling frame to an actuator166of the install device130.FIG. 7shows the relationship between the coupling frame162and the jetting module48when the coupling frame is fully retracted away from the jetting module48. The coupling frame162would be in this position whenever the install device130is not latched to the printhead frame146, for example such as inFIG. 5. In this embodiment, the actuator166comprises a motor actuator, but other actuators could he employed such as over-center linkage systems or the like. The compliant coupling of the coupling frame162enables the coupling frame162to align itself with the jetting module48so that necessary fluid and electrical connections can be made to the jetting module48without compromising the integrity of the kinematic mount of the jetting module48to the printhead frame146. The coupling frame162includes first guiding features168that engage corresponding second guiding features170of the install device130. These guiding features168and170serve to pre-align the coupling frame162to the jetting module48. The detents140mentioned earlier that center the jetting module48within the pocket135of the install device130also serve to ensure that the coupling frame162is pre-aligned to the jetting module48.

FIG. 8illustrates the respective relationships of the coupling frame162and the jetting module48as the coupling frame162has been displaced toward the jetting module48by the actuator166. The coupling frame162is beginning to engage the jetting module48. As shown, the coupling frame162includes alignment posts172that engage corresponding recess portions174of the jetting module48to align the coupling frame162to the jetting module48. Once the alignment posts172engage the corresponding recesses174of the jetting module48, it is no longer necessary for the coupling frame162to be guided by the pre-alignment guiding features168. The diameter of the upper portion168aof the guiding features168is smaller than the diameter of the lower portion168bof the guiding features168to provide additional clearance between the first guiding features168and the corresponding second guiding features170of the install device130so that the guiding features168no longer serve to align the coupling frame162when the posts172of the coupling frame162engage the corresponding recesses174of the jetting module48.

FIG. 9shows the coupling frame162contacting the jetting module48to make all the required fluid and electrical connections,178and180respectively. O-rings176are used to produce leak free seals at the fluid connections178between the coupling frame162and the jetting module48. The electrical contacts of the coupling frame162comprise spring biased contact pins182(seeFIG. 7). The length of the contact pins182can he varied as shown inFIG. 7to ensure that the various electrical connections are made in the desired sequence order.

Referring toFIG. 10, there is shown the jetting module48in the pocket135of the install device130. The jetting module is also located in a receiving receptacle147of the printhead frame146with the alignment features156of the jetting module engaging the corresponding alignment features158of the printhead frame146. (The drop deflection mechanism is not shown to enable the relationship between the jetting module48, printhead frame146and the install device130to he seen.) The second latch device160of the latch mechanism144of the install device130engages the mating portions148to secure the install device130to the printhead frame146. The coupling frame162is shown lowered into position to provide the fluid and electrical connections to the jetting module48. The coupling frame162provides downward force to the jetting module48to hold the jetting module in place with the alignment features156of the jetting module48properly engaging the corresponding alignment features158of the printhead frame146. The install device130may include one or more signal indicators, such as sensors or switches, to provide signals to the printer controller (not shown) as to the install condition of the jetting modules48. For example switch184is used as first signal indicator to signal that the install device130is latched to the mating portions by the second latch device160. Similarly, electrical signals passing through the coupling frame162to the jetting module and back to the coupling frame162through the electrical connections can serve as a second signal indicator to signal that the coupling frame162is properly coupled to the jetting module48. When the coupling frame162is fully retracted from the jetting module48(not the state shown inFIG. 10) the end of the first guiding feature168, which is attached to the coupling frame162, will protrude through second guiding member170of the install device body to contact switch186, which then provides a signal indicating that condition to the controller. The printer controller may use such signals to ensure the install/uninstall sequences are progressing properly. For example, the printer controller that controls the fluid system can impede the flow of ink to the coupling frame when a first signal indicator indicates the jetting module is not properly secured to the printhead frame and the second signal indicator indicates that the coupling frame is not properly coupled to the jetting module. Similarly, when the printer controller receives signals from the fluid system that fluid is being supplied under pressure to a jetting module, it can act to prevent the actuator166displacing the coupling frame away from the jetting module.

Parts List