The present invention relates generally to micro-fluid ejection devices. Particularly, it relates to modular components and systems and methods for assembling same.
Conventional micro-fluid ejection devices, and more particularly ink jet printers, include a printhead carrier that carries one or more printheads. Such printheads have one or more local or remote fluid reservoirs in fluid communication with nozzles through which fluid exits the printhead toward a print medium. The nozzles are located on one or more ink jet chips.
The carrier is guided by one or more guide members, for example, a guide rod or tab. The guide members define a bi-directional path called the scanning direction. During printing, a controller directs the carrier to move in a reciprocating manner, back and forth along the guide members in the scanning direction. The movement transports the printhead(s) across the width of a print media as the media advances in a sub-scan direction orthogonal to the scanning direction. This allows the printhead(s) to eject fluid to image an entirety of the media.
When fashioning together multiple printheads, precise alignment on the carrier is critical for properly registering fluid drops on the media. Any skew from one printhead to the next manifests itself in poor image quality. In imaging devices having stationary printheads, such as those found in page-wide arrays, the problems are only exacerbated. Multiple aligned nozzle plates are required to cover the breadth of the media and each requires registration in the translational and rotational dimensions relative to every other plate. Precision during component manufacturing and alignment during assembly begins the registration process and early errors become compounded during later printing.
Accordingly, a need exists in the art for improving image quality where multiple printheads are used. The need extends not only to better controlling alignment and registration of printheads, but to manufacturing and assembly. Additional benefits and alternatives are also sought when devising solutions.
The above-mentioned and other problems become solved with modular micro-fluid ejection devices. In a first embodiment, a carrier frame commonly mounts a plurality of ejection modules. Each module has a plate of nozzles defining a plane. Adjacent plates are substantially coplanar and registered with one another across an entirety of the frame. Print quality in lengthy arrays is improved. Representative mounting parameters contemplate less than about 0.20 degrees of rotation about the short and long in plane axes about the nozzle plate. In various designs, adjacent nozzle plates overlap one another on the frame or are spaced. Overlapped modules may include interlocking surfaces to facilitate placement. Nozzles of the plates may also align collinearly.
In other embodiments, each module fits within a thickness or rests on rails of the carrier frame. A first adhesive temporarily mounts an undersurface of a module ledge to a top of the frame. A second, more durable adhesive permanently mounts the modules to an inner surface of the thickness or rails. The first adhesive typifies epoxies or glues that can set or cure quickly to hold the precisely aligned modules temporarily in place. Curing of the first adhesive may include ultraviolet curing. Alternatives include thermal, infrared and microwave curing. The second adhesive typifies materials affording long term mechanical and functional stability. Dispensing the first adhesive occurs with limited physical exposure, such as in the form of discrete dots placed on particular frame surfaces. Dispensing the second adhesive occurs more liberally to multiple locations at a same time. In some embodiments, curing of the second adhesive occurs at room temperature.
Manufacturing systems include suction devices to hold a first module in place on a fixture while later modules are suctioned and registered to each other. A substantially planar surface of the fixture keeps modules aligned vertically, while horizontal adjustments occur manually or robotically. Once all are set in place, a carrier frame is commonly contacted to the modules and the suction released. After cure, the adhesives between the frame and modules cause the modules to separate from the fixture and transfer to the frame. All remain properly registered after the transfer. A pump supplies the suction and holes in the fixture fluidly connect to the pump. The pump selectively suctions individual modules onto the fixture. First and second adhesives are also contemplated to temporarily and permanently attach the modules to the frame. Portions of the fixture may be transparent to ultraviolet radiation. Alternatively, the fixture includes a window to pass radiation during curing.
In still further embodiments, the system includes spacers for mounting on the fixture member to contact individual modules. Each spacer has a substantially planar surface and a hole to align with one of the holes in the fixture member. Each spacer is configured to receive an adhesive on a side surface to mount the spacers to the fixture member. The spacers have a common thickness.
These and other embodiments will be set forth in the description below. Their advantages and features will become readily apparent to skilled artisans. The claims set forth their particular limitations.
The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention. Together with the description, they serve to explain the principles of the invention. In the drawings:
a is a plan view of a plurality of micro-fluid ejection modules having horizontal skew relative to one another;
b is a diagrammatic view of micro-fluid ejection modules having misalignment relative to one another;
c is a side elevation view of a plurality of micro-fluid ejection modules having vertical skew relative to one another;
d is a diagrammatic view of micro-fluid ejection modules having misalignment relative to one another;
In the following detailed description, reference is made to the accompanying drawings. Like numerals represent like details. The embodiments enable those skilled in the art to practice the invention. Other embodiments may be utilized and process, electrical, and mechanical changes, etc., may be made without departing from the scope of the invention. The following is not to be taken in a limiting sense and the scope of the invention is defined only by the appended claims and their equivalents. In accordance with the present invention, methods and apparatus include modular micro-fluid ejection devices.
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A module 20 typically includes a fluidic ejection device such as a heater chip 26 or a piezo ejection device. The chip resides beneath the nozzle plate and fluid firing elements cause fluid to eject through individual nozzles, as is known. The chip is formed as a series of thin film layers in combination with the nozzle plate or the plate independently attaches after formation of the chip. Also, modern designs contemplate fanning out fluidic connections downward from the chip through various manifolds. The fan-out includes one or more layers of silicon, ceramic, liquid crystal polymer, or the like. A printed circuit board (PCB) (such as a Stablcor brand carbon fiber laminate), along with flexible circuits are provided to make electrical connections to energize the firing elements during use. Wire or TAB bonds and associated encapsulants may also form part of the module 20 when completing the circuits. In the design shown, the module has a printed circuit board 28, a silicon manifold 30, a flex circuit 32, a silicon tile 34 and a ceramic base 36. The parts are attached or molded into the module 20 by conventional means to allow the module to eject fluid (e.g., ink) from a reservoir (not shown) toward a print medium. Also, the module may be designed in a fashion to operate as a heat sink to remove heat from the heater chip to allow for faster printing. Specific proposals illustrating fluidic fan-out can be found in the Applicant's co-pending U.S. patent applications (Ser. Nos. 12/624,078, filed Nov. 23, 2009, and 12/568,739, filed Sep. 29, 2009), both of which are incorporated herein by reference.
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The carrier frame 50 is made substantially of metal, plastic or any other suitable material. Thermal properties, stiffness, weight and conductivity are a few of the considerations skilled artisans will recognize when selecting a material. In size, the modules form a layout that operationally extends at least as wide as a desired print medium. If a desired media for imaging is 8½ inches×11 inches, the fluid ejecting zone of the modules may span (S) at least 8½ inches across the frame or scan to this same distance. Alternatively, the span (S) may range from a few inches for use in the field of “coupon” or “receipt printers” to thirty six inches or more for printers involved in imaging banners or other lengthy substrates. Alternatively, the modules form a layout that is less than the width of a desired print medium and the ejection device moves bi-directionally in the scanning direction across the width of the print media.
In order to permit precise ejection of fluid from the ejection device, it is necessary to precisely locate the nozzle plates 22 of all modules in three dimensions. In some embodiments, the heights of the nozzle plates relative to a top of the frame are substantially the same such that each is substantially coplanar with one another (z-dimension). Further, the nozzle plates are registered with one another such that the x and y axes defined by each nozzle plate are substantially parallel with one another. The precise arrangement allows for optimal print quality.
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In any of the foregoing, methods for assembling the ejection device of the present invention contemplate conventional assembly tools. In a representative situation, the carrier frame is loaded into a pick and place tool. A first of the ejection modules is then picked and mated with the frame. The pick tool comprises a vacuum chuck and/or robotic arms that contact the module in the vicinity where no nozzles of the nozzle plate are present. In some embodiments, the first ejection module is mated with an opening in the carrier frame. Alternatively, the module is mated on multiple rails. Alternatively still, the module is preconfigured with the first adhesive or the first adhesive is applied after the pick. The module is moved toward the carrier frame and placed face up (nozzles up) into the first adhesive. In some embodiments, the module is pressed into the thickness of the adhesive dot but not so far as to squeeze out the adhesive and cause contact with the carrier frame. This ensures that the maximum tolerance stack up is accounted for such that the height of each module on the carrier frame is the same. The first adhesive 60 is then cured, such as by applying ultraviolet radiation. The pick and place tool remains engaged with both the carrier frame and the first module during this time to maintain proper positional alignment. Similarly, a second module is temporarily cured in place on the carrier frame with the first adhesive. A second, durable adhesive is then applied to all the modules and/or frame to permanently affix them in place. The properties of the second adhesive allow a rigid interconnection between the modules and frame.
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In some embodiments, the system further includes a plurality of spacers 114 for mounting on the fixture member 110. Each spacer 114 has a substantially planar surface and a hole 116 configured to fluidly align with one of the holes 112 in the fixture member. The holes 116 are configured to suction ejection modules to temporarily hold the modules in place against the spacers, while the planar surface keeps planar the nozzle plates of adjacent modules. In certain configurations, the holes 116 are approximately 0.5 mm in diameter. Their size takes into account the available area for suctioning the top side of each module without contacting the nozzles in the nozzle plate. It also considers the magnitude of the suction force to be applied in order to ensure that sufficient force is applied to hold the modules while also avoiding excessive force that could damage the module. In composition, the spacers typify silicon from a common wafer such that each has a precisely matched thickness to mount each module in a common plane. To keep each spacer on the fixture member, it is contemplated that an adhesive 118 will be applied to a side surface 115 of each spacer so that a height of each spacer above the fixture member will remain true to the thickness of the spacer. Alternatively, the spacers may be attached to the fixture member with a bondline on a backside surface and then co-polished together to a common height. Additional alternatives include those where, in place of spacers, portions of the surface of the fixture member adjacent to the suction locations are recessed to avoid contacting the nozzles of the modules. This may be accomplished by etching recessed areas into a fixture member comprised of photostructurable glass.
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The fixture member is then separated from the ejection modules to transfer them to the carrier frame 50 with proper registration and planarity relative to one another. The use of a fixture member in this manner allows mating of all modules with the carrier frame at one time rather than one module at a time. Separating the ejection modules includes releasing the suction applied by the pump 120 and removing the fixture member. The modules 20 are then permanently adhered to the carrier frame 50 by application of the second adhesive 62. Alternatively, the application of the second adhesive can occur before separation of the fixture member. Alternatively still, the locating surface 111 of the fixture member can be oriented face down and the modules delivered face up, in contrast to the figures. In this way, the assembly system prevents dust from settling on the locating surface of the fixture member which may otherwise adversely affect the height and/or planarity of the modules.
The foregoing has been presented for purposes of illustrating the various aspects of the invention. It is not intended to be exhaustive or to limit the claims. Rather, it is chosen to provide the best illustration of the principles of the invention and its practical application to enable one of ordinary skill in the art to utilize the invention, including its various modifications that naturally follow. All such modifications and variations are contemplated within the scope of the invention as determined by the appended claims. Relatively apparent modifications include combining one or more features of various embodiments with one another.