Patent Application
20120306974
The present invention relates to micro-fluid applications, such as inkjet printing. The invention relates particularly to detecting fluid levels in supply items consumed in micro-fluid applications. Capacitive sensing with on board processing facilitates designs as does pump enable circuitry.
The art of printing images with micro-fluid technology is relatively well known. A disposable or (semi)permanent ejection head has access to a local or remote supply of fluid (e.g., ink). The fluid ejects from an ejection zone to a print media in a pattern of pixels corresponding to images being printed. Accurately knowing fluid levels in supply items aids printing.
Yet, as printing evolves away from individual dedicated printers toward workgroup environments, users no longer man printers and note supply item volumes. If ink levels are incorrectly reported, network users potentially print pages before realizing empty supply items require replacement. Incorrect reporting also leads potentially to “dry firing” the ejection head and ingesting air in fluidic channels.
Also, ejection heads are now commonly separated from their ink source. While this helps reduce consumer costs by avoiding the repeated sale of silicon chips, and allows consumption of larger volumes of ink with fewer instances of replenishment, it necessitates the ink source to maintain some form of identification that it can report to printers. In turn, printers use the information to ascertain fluid levels, such as by counting algorithms in firmware that note drops ejected, firing commands initiated or other factors such as fluid evaporation over time. Printers notify users through sensors or display messages that their supply item is empty or nearing empty. Over the years, these algorithm schemes have ranged from slightly incorrect to exceptionally faulty. They have also proven ineffective upon fluid refilling. Users regularly ignore their results and warnings.
Still other detection schemes sense fluid by means of capacitors, optics, weight, ultrasound, magnets, floats, torque sensors, electrical probes, or the like. Many require some form of stimulus external to the supply item. The latter adversely complicates control systems between supplies and their corresponding printers. Many also involve one or more of the following: complex calibration schemes; process to ascertain variations in printer electronics and cabling tolerances; noisy signals resultant from lengthy conductive traces and remotely located circuit components; and inability to move supply items from one printing device to a next.
Accordingly, a need exists in the art to improve fluid level detection in supply items of imaging devices. The need extends not only to improving accuracy, but to simplicity in complex networked environments. Economic advantage is still another consideration. Additional benefits and alternatives are also sought when devising solutions.
The above-mentioned and other problems become solved with consumable supply items having fluid sensing for micro-fluid applications. The supply item determines fluid levels with capacitive sensing and undertakes on board signal processing. It supplies the processed signal to an imaging device for accurate tracking of supply item fluid levels. No longer do imaging devices conduct processing operations and current fluid levels can remain fixed with the supply item as it travels from one device to the next as necessary. The supply item is also tightly calibrated to remove variability in electronic components and cables, or the like.
In a representative embodiment, the supply item holds an initial or refillable volume of ink. Its housing defines an interior having a pair of opposed electrodes. The electrodes define a capacitance that varies in response to an amount of liquid between them. A controller energizes one electrode and receives an output reading from the other. The controller processes the reading on board the housing and supplies it as a digital data stream to the imaging device during use.
Processing of the signal includes amplification, filtering, synchronization, and analog to digital conversion, among others, and is undertaken with compact analog circuit components. It improves signal to noise ratios over conventional techniques. A memory stores calibration values for an empty and full housing. The imaging device correlates the calibration values to a present output reading of the supply item to accurately know present fluid levels or identify tilt (improper installation) of the supply item. The controller writes back to the memory present fluid levels obtained from the output reading of the electrode.
In other embodiments, the controller defines an enable output to allow operation or not of a fluid pump in the imaging device. In this manner, the pump only operates if the supply item is properly installed, has fluid and is not otherwise tilted out of position. It prevents de-priming ejection printheads, dry firing the heads, spilling over ink, and operating fluid pumps without fluid.
In still other embodiments, a modular construction contemplates a front piece attached to the housing. The piece co-locates the electrodes, controller, and memory and provides interfaces for communicating with the imaging device. Interfaces include, but are not limited to, a digital data stream output corresponding to the present fluid level reading and a pump enable. The front piece also contemplates construction with polypropylene or polyethylene materials that over coat electrodes of tin-plated steel. The piece welds to a front opening of the housing to vertically orient the electrodes to detect fluid in the housing interior. The electrodes extend from the coating in at least two locations. A first location is used to grasp the electrodes during the coating process, while the second location is used to energize the electrodes or receive its output reading during use. The front piece also locates communication ports for the transfer of fluid back and forth to the imaging device and to provide a source of air for overcoming backpressure. The front piece also defines a common size that can fit on any sized housing to allow varying fluid volumes in differing imaging operations. The front piece and/or housing may include still other structures useful in fluid mechanics, such as venting openings, valves, filters, standpipes, fittings, etc.
These and other embodiments are set forth in the description below. Their advantages and features will be readily apparent to skilled artisans. The claims set forth particular limitations.
The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:
In the following detailed description, reference is made to the accompanying drawings where like numerals represent like details. The embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that other embodiments may be utilized and that process, electrical, and mechanical changes, etc., may be made without departing from the scope of the invention. The following detailed description, therefore, 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 features of the invention, methods and apparatus include consumable supply items having fluid sensing for micro-fluid applications, such as inkjet printing, medicinal delivery, forming circuit traces, misting water, etc.
With reference to
The housing material is any of a variety for holding fluid. It comprises glass, plastic, metal, etc. Techniques for producing the housing envision blow molding, injection molding, etc. as well as welding, heat-staking, gluing, tooling, etc. Selecting the materials and designing the production, in addition to ascertaining conditions for shipping, storing, use, etc., includes further focusing on criteria, such as costs, ease of implementation, durability, leakage, and the like.
The overall shape of the housing is varied. It is dictated by an amount of fluid to be retained and good engineering practices, such as contemplation of the larger imaging context in which the housing is used. In the design given, the housing is generally rectangular and sits vertically upright. It holds a volume of ink on the order of about 450 ml in a container defining a capacity of about 500 ml. It has a height of about 120 mm. In smaller designs having the same height, the ink volume is about 150 ml in a capacity of about 180-190 ml.
The walls of the housing have a thickness “t.” They are generally the same thickness everywhere about an entirety of the housing. They are sufficiently strong to maintain the shape of the housing throughout a lifetime of usage. They are rigid enough to preventing bowing, tilting and the like. They are not overly thick to waste material. The thickness ranges from about 1.0 to about 2.0 mm. The walls may be also formed as a unitary structure in a single instance of manufacturing or as pieces fitted together from individual parts. The latter envisions a modular construction.
In other modular constructions, a front piece or nose piece 33 is contemplated to weld close an opening 35 of the housing. In this way, the volume and size of the housing can be made variable, while the nose piece can provide a constant interface to an imaging device. It enables the size of the housing walls to vary as demand dictates, but overall manufacturing only changes by the amount necessary to make the walls different sizes. The construction of the nose piece, ports and tooling remains the same from one product offering to the next. This saves costs while allowing many differently sized products. The interface also includes a circuit board 37 attached to the nose piece to conduct on board processing. It has a front side 29 defining conductive pads 39 for electrically communicating to an imaging device. It has a backside 41 defining locations for a controller 27 and other electronic components, as necessary, for signal processing aboard the supply item 10 (see also
In either the modular or integral design, the housing supports a pair of opposed electrodes 50, 52. They are situated to detect a fluid level in the housing. They are conductive plates whose capacitance varies upon the application of electrical energy according to an amount of liquid that exists between the electrodes. With greater amounts of fluid, the plates have a greater amount of capacitance. With lesser amounts of fluid, the plates have a lesser amount of capacitance. The plates are generally parallel and are distanced from one another in a range of about 4 to about 10 mm.
The plates are also steel plates with a thin coating of tin. The steel ranges in thickness from about one to about ten mm. The tin ranges in thickness from foil thinness to that of a few millimeters. In turn, the tin is over-molded with a fine layer or coating of a non-conductive material, such as polypropylene or polyethylene. The coating ranges up to about 1.5 mm. Similarly, too, the nose piece is formed of a non-conductive material, such as polypropylene or polyethylene. Alternatively, the fine coating is eliminated and coatings on the plates are subsumed within the materials of the nose piece.
The plates electrically connect to the controller 27 on the backside 41 of the board 37 by way of conductive prongs 45, 43. The prongs extend through the nose piece. With reference to
Also, on board processing of the output reading is undertaken at the supply item before supplying to the imaging device. First, an amplifier 120 is used to increase a signal level of the output reading. This improves signal to noise ratios of the output reading. Second, the amplified signal is filtered at 130 to eliminate further extraneous noise. At 140 and 150, a synchronous rectifier and synchronizer act in concert to coordinate the frequencies of the input 101 and output 103 that reside on opposite electrodes 50, 52 of the electrode pair. At 170, the controller 27 supplies the input 101 as a pulse width modulated square wave. At 160, a converter changes the output reading from an analog reading back into a digital signal. As a noted advantage, keeping together the components of this system on the supply item allows for co-location of analog components and short lengths of electrical traces. In turn, electromagnetic radiation is kept at a minimum as is electrical susceptibility to noise which is otherwise common in analog circuits. The controller 27 also alters the digital signal into a digital data stream (16 bit) for supplying to the imaging device on (data) pad 39-3.
On other pads, power and ground 39-1, 39-4 are made common between the supply item 10 and the imaging device. Similarly, a clock is provided from the imaging device at pad 39-2 to synch the signals received from the controller 27.
At pad 39-5, a pump enable output is provided to the imaging device from the supply item. Appreciating that some imaging devices will have fluid recirculation systems, the enable output allows operation or not of a fluid pump in the imaging device. The concept is to prevent spilling over fluid in the imaging device by operation of a fluid pump, until such time as a supply item is properly installed and can receive return fluid, such as at port 11 (
The controller 27 of the supply item and the controller of the imaging device also coordinate with one another to ascertain fluid levels in the supply item at any given point in time. With reference to
If the fluid level is not depleting at S220, it may be the situation that the fluid level is increasing, such as if a major tilt were introduced in the imaging device and fluid greatly filled the space between the electrodes. In such a circumstance, the pump of the imaging device should be turned off or otherwise made disabled and the user notified, S230. This prevents fluid spill in the imaging device or other unfortunate consequences, such as de-priming ejection heads, cross contaminating the inks at the ejection head, or ingesting air in liquid channels. The disabling of the pump occurs by the controller altering the voltage level on the enable output pad 39-5 back to voltage high. Notifications to the user occur by way of display screen messages, audible alarms, visual light patterns, or the like. On the other hand, if the fluid level at S220 were not found to be increasing, the present fluid level may the same as an earlier fluid level and operation of the imaging device can continue unabated. The new level can also be logged, time stamped, etc. at S240. The logging can occur in the controller 27 by writing back to memory the present fluid level. Alternatively, or in addition, the present fluid level can be stored in the imaging device. In either, the imaging device remains available to users for printing at S250.
At S260, if the fluid level is actually depleting at S220, the controller determines whether the supply item is empty. If so, the pump is again disabled to prevent problems in the imaging device and the user is notified at S230. If the supply item is not empty, but simply depleting, the new lower level of fluid is logged at S240 and the imaging device is maintained available for printing at S250.
With reference to
Upon installation in an imaging device, the imaging device can use the empty and full condition values read from memory of the supply item to calibrate its expectations of readings supplied to it from the supply item. For instance, if a full condition for a first supply item corresponded to 11.0 pf and an empty condition corresponded to 1.0 pf, the imaging device could set an expectation of a half full supply item to occur around 6.0 pf, or halfway between 11.0 pf and 1.0 pf. Conversely, if a later installed second supply item had full and empty values corresponding to 11.5 pf and 1.5 pf, the half full supply item would be expected by the imaging device to occur at 6.5 pf, which is halfway between the 11.5 pf and 1.5 pf readings. In any scheme, this process eliminates fluid fill variations that are due to one or more of the following (but not limited to): manufacturing fill tolerances; variations in the dimensions/volume of the supply item; variations in fluid composition from one batch to a next; variations in electrical components and electrodes from one supply item to the next; and variations owing to future implementations of fluid, materials, electronics, or the like.
As part of the overall assembly at S300, each of the opposed electrodes 50, 52 (
In still other considerations of the electrodes, fluid level detection is improved as signal to noise ratios are increased. To achieve this, the plates of the electrodes are entirely conductive and made as large as practicable. The plates are also made the same shape and placed parallel to one another inside the interior 14 of the housing 12 as seen in
Firstly, charges on the metal cause constituents to flocculate out of the fluid and collect on the plates, especially with pigment based inks. This collection causes degradations over time in the strength of signal of output readings (103) of the electrodes. Secondly, stainless steel remains durable in liquid, but is relatively expensive. A preferred solution, therefore, is embedding the plates within a non-conductor, such as a plastic housing, which allows the plates to charge without attracting fluid ingredients and prevents direct contact with fluid, thereby enabling a vaster selection of materials beyond that of stainless steel. In turn, cheaper materials are available as are materials that can be soldered into electrical communication in a circuit, unlike stainless steel.
A mold over the plates also enables the precise placement of the non-conductor, but also controls plate to plate spacing within prescribed molding tolerances, keeps the plates in one single, modular piece to reduce part variations, and minimizes air gaps between the plates which leads to distorted fluid level readings. In addition, the use of an over-molded design preserves plastic tool life by reducing the risk of thin steel conditions (that could exist from forming pockets to press-fit the plates) and allows for lengthier plates, thus larger surface area that increases signal strength.
Relatively apparent advantages of the many embodiments include, but are not limited to: (1) a supply item having self-contained fluid level detection device, including on-board processing, memory and digital messaging; (2) pump enable or disable dictated by the supply item; (3) a calibration process for empty/full levels of the supply items during manufacturing yielding calibration of individual imaging devices; (4) fluid level detection using capacitive plates inside the fluid to increase accuracy; (5) modular designs facilitating mass production, ease of circuit placement, and compatibility with multiple fluid filling levels and volume sizes.
The foregoing illustrates various aspects of the invention. It is not intended to be exhaustive. 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. Relatively apparent modifications include combining one or more features of various embodiments with features of other embodiments.
