Patent Publication Number: US-6908183-B2

Title: Fluid ejecting methods and related circuits

Description:
BACKGROUND 
     Existing ink jet printing devices employ complex circuitry and components to enable hundreds of fluid-ejecting devices to be fired cooperatively to achieve a desired image. However, many applications for fluid-ejecting devices have remained undeveloped because of the expense of such circuitry and components. Many applications for fluid-ejecting devices do not utilize the selective control utilized in an ink jet printer. Similarly, many potential applications can employ fewer, or in some cases, a single fluid-ejecting device(s). For such applications the existing circuitry and components for energizing the fluid-ejecting devices can be unnecessarily complicated and prohibitively expensive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The same components are used throughout the drawings to reference like features and components. 
         FIG. 1  shows a cross-sectional view of an exemplary fluid ejecting device in accordance with one embodiment. 
         FIG. 2  shows a perspective view of an exemplary print cartridge in accordance with one embodiment. 
         FIG. 3  shows a diagrammatic view of an exemplary consumer device in accordance with one embodiment. 
         FIG. 4  shows a block diagram of components of an exemplary circuit in accordance with one embodiment. 
         FIGS. 5-5   a  show diagrams of components of an exemplary circuit in accordance with one embodiment. 
         FIG. 6  shows a diagram of components of an exemplary circuit in accordance with one embodiment. 
         FIG. 7  shows a flow diagram indicating acts in an exemplary method in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     The embodiments described below pertain to energizing circuits. In some embodiments, suitable energizing circuits can store energy from a battery and ultimately deliver a pulse of energy sufficient to activate an energizing element of a fluid ejecting device. Activation of the energizing element causes fluid to be ejected from the fluid ejecting device. 
     First Exemplary Embodiment 
       FIG. 1  shows cross-sectional view of an exemplary fluid-ejecting device  10  formed in a substrate  12 . A firing chamber  14  is formed in the substrate and receives fluid in one portion of the firing chamber (shown generally at 16) and ejects fluid from another portion of the firing chamber (shown generally at 18). An energizing element  19  proximate the firing chamber  14  can energize the fluid contained therein to cause a portion of the fluid to be expelled. Examples of energizing elements  19  include firing resistors and piezoelectric crystals among others. 
     A fluid ejecting device ejects fluid when a sufficient pulse of energy is supplied to activate the fluid ejecting device&#39;s energizing element. Once the energizing element has been activated, fluid is ejected and a period of time is allowed for the fluid ejecting device to refill before the next pulse is supplied. Various suitable fluid ejecting devices utilize varying energizing sequences as will be recognized by the skilled artisan. 
       FIG. 2  illustrates a print cartridge  20  which is a commonly recognized use of fluid-ejecting devices  10   a . Such a print cartridge is configured for use in various consumer devices such as an ink jet printer. In such an application, multiple fluid-ejecting devices  10   a  are positioned on a print head  22 . In various applications, the fluid-ejecting devices are selectively energized by a processor, a controller, a print head driver circuit, a controlled voltage power supply, and related circuitry coupled to the print head to cooperatively form a desired image on a print media. An example of such a configuration is shown at U.S. Pat. No. 6,183,046. 
     Many potential consumer devices can utilize fluid ejecting devices as advantageous fluid delivery systems. A consumer device can be any product available to consumers either for personal or business applications. One such exemplary consumer device is described in relation to FIG.  3 . 
       FIG. 3  shows a consumer device embodied as an air brush  30 . The air brush  30  includes a power source that, in this embodiment, comprises a battery  32 . The air brush  30  also comprises an energizing circuit  34 , a switch  35 , an ink reservoir  36 , and a fluid-ejecting device  10   b  for ejecting ink  38 . The various components can be positioned in a housing  39 . 
     A user can control the function of the air brush  30  via the switch  35 . When the user closes the switch  35 , electrical energy can flow from the battery  32  through the energizing circuit  34 . The energizing circuit activates the fluid ejecting device  10   b  to eject ink  38 . The user can, as desired, open the switch to stop ink flow. 
     In this configuration, the air brush  30  is self-contained and portable. It can be utilized for applying ink or other fluids to a surface without physically contacting the surface. Such a configuration is desirable for artistic applications, among others. 
       FIG. 3  represents but one suitable consumer device utilizing a fluid ejecting device. Many other suitable applications include devices that can utilize similar fluid ejecting devices. For example, other consumer devices may be utilized to deliver various liquids in a laboratory setting. In one such embodiment, a desired amount of a reagent can be dispensed where the fluid ejecting device ejects a generally consistent volume of fluid when the energizing element is activated. The device can then be activated an appropriate number of times and/or for a given duration of time to deliver a desired volume of fluid. Such devices can be advantageous in that no contact is required to deliver the fluid from the fluid ejecting device, thereby reducing the chance of contamination. In some applications, the consumer devices may be inexpensive enough to allow them to be used in a disposable manner. 
       FIG. 4  shows an overview of the functional components of one exemplary energizing circuit  34   b  comprising a direct current (DC) power source such as a battery  32   b , an oscillator  44 , an energy storage device  46 , and an energizing element  19   b . The battery  32   b  is connected to the oscillator  44  that converts the DC power from the battery to alternating current (AC). The oscillator  44  delivers power to the energy storage device  46  which can comprise an inductor, a capacitor, or a capacitor in combination with an avalanche device, among others. The energy storage device  46  stores a desired amount of energy that is subsequently delivered to energizing element  19   b  as a suitable pulse of energy to activate the energizing element. 
       FIGS. 5 and 6  show exemplary energizing circuits. Each of the energizing circuits stores energy from a power source and can deliver the stored energy as a pulse of energy suitable to activate an energizing element of a fluid ejecting device sufficient to cause fluid to be ejected therefrom. 
       FIG. 5  shows an exemplary energizing circuit  34   c  that comprises a power source comprising a battery(s)  32   c , an oscillator  44   c , an energy storage device comprising a capacitor  52 , an avalanche device comprising a diac  54 , and an energizing element comprising a firing resistor  19   c . The battery  32   c  is electrically coupled to the oscillator  44   c  that is coupled in parallel with the capacitor  52  and the energizing element  19   c . The diac  54  is positioned in series between the capacitor  52  and the firing resistor  19   c.    
     Various suitable battery(s)  32   c  can be utilized. Some exemplary embodiments can utilize standard, commonly available batteries such as one or more 1.5 v (volt) “AA” penlight batteries, among others. Such readily available batteries can provide an added degree of convenience for a user. Other battery types and/or voltages can provide suitable embodiments as will be recognized by the skilled artisan. Though a battery is utilized as the power source in the described embodiments, other suitable power sources, such as capacitors or fuel cells, can also be utilized in place of, or in combination with a battery(s). 
     The oscillator  44   c  utilized in  FIG. 5  can be any suitable oscillator or similar functionality. The characteristics of the oscillator can be selected depending on the voltage of the power source and the specifications of the energizing element among other. For example, if a relatively low voltage power source like a 1.5 v battery is utilized, an oscillator capable of stepping-up the voltage can be utilized. One such suitable oscillator will be described in more detail below in relation to  FIG. 5   a . Other suitable embodiments can utilize a battery having a higher voltage and thus may or may not utilize an oscillator having step-up capabilities. 
     In the embodiment shown in  FIG. 5 , DC energy is supplied from the battery  32   c  to the oscillator  44   c  which converts the energy to AC and in this case steps up the voltage. The AC energy charges the capacitor  52 . In this embodiment, the oscillator  44   c  charges the capacitor  52  until the voltage across the capacitor reaches a predetermined value of the diac  54  which is a voltage sensitive switch. As such, when voltage is applied to the diac, it remains in a turned off state until the voltage reaches the predetermined value (which in this embodiment is 40 v) at which point it turns on or fires. At this point the diac  54  displays a negative resistance and the energy stored in the capacitor  52  flows through the diac  54  and the energizing element  19   c  until a second lower value of the diac is reached, at which point the diac turns off and flow stops. The capacitor  52  begins to recharge allowing time for the fluid ejecting device to refill before the process is repeated. Though a diac is utilized in this embodiment, other suitable embodiments can utilize other avalanche devices such as Zener diodes and Shockley diodes, among others. 
     In the embodiment shown in  FIG. 5 , the capacitor  52  comprises a 0.6 microfarad capacitor and the diac  54  has a 40 v potential. Other suitable embodiments can utilize other values depending on the properties of the various components comprising a suitable energizing circuit. The frequency of triggering the avalanche device (diac) followed by recharging the capacitor can be controlled, at least in part, by the frequency of the oscillator, and the value of the capacitor. Various firing rates of the fluid ejecting device&#39;s energizing element can be utilized. For example, some embodiments can utilize an energizing element that functions at about 20 kHz. Some other embodiments can utilize an energizing element that function at about 40 kHz. Still other embodiments can utilize an energizing element that function at a value between about 20 kHz and about 40 kHz. Further embodiments can utilize energizing elements that function outside of these values. Suitable components can be combined to achieve a desired firing rate. 
       FIG. 5   a  shows a more detailed view of an exemplary oscillator  44   c  as shown in FIG.  5 . In this embodiment, the oscillator comprises a transformer  55 , a resistor  56 , a diode  58 , and a transistor  59 . The transformer  55  has a primary (p 1 ) coupled to the positive side of the battery  32   c  (shown FIG.  5 ). The positive side of the battery is also connected to the transformer&#39;s secondary (S 2 ) via the resistor  56 . The transformer&#39;s other secondary (s 1 ) is connected to the capacitor  52  (shown  FIG. 5 ) via diode  58 . The transformer&#39;s center tap (ct) is connected to the base of npn transistor  59 . The collector of the transistor  59  is connected to the transformer&#39;s other primary (P 2 ). The emitter of the transistor  59  is connected to the negative side of the battery  32   c  (shown  FIG. 5 ) and the opposite pole of capacitor  52  (shown  FIG. 5 ) as the transformer&#39;s secondary s 1 . 
     In the oscillator  44   c  shown in  FIG. 5   a , the transistor  59  pulses on and off making the transformer  55  oscillate. The transformer has a split winding on the right hand side that feeds the base of the transistor  59 . Though an npn transistor is shown here, similar functionality could be achieved with a MOSFET, among others. This exemplary configuration provides feedback through the transistor that turns the oscillator off. The transistor subsequently stops providing feedback and the oscillator turns back on. 
     The transformer  55  can produce a desired secondary voltage depending on the “turns ratio” of the transformer as will be recognized by the skilled artisan. The output of the oscillator  44   c  charges the capacitor  52 ; the diode  58  prevents discharge back through the oscillator. In one particular embodiment, the transformer output from the secondaries (s 1  and S 2 ) is a higher voltage than the diac  54 . In this embodiment, the diac directly controls the flow of energy into the energizing element  19   c , though other embodiments can utilize a silicon controlled rectifier “SCR” positioned between the diac  54  and the energizing element  19   c . The SCR can be connected between the diac and the energizing element so that the diac would trigger the SCR that would then activate the energizing element with a higher current. 
     In this embodiment, the energizing circuit  34   c  provides a desired, controlled amount pulse of energy to the energizing element  19   c . The value of the energy pulse is controlled by the capacity of the capacitor  52  which can store a given amount of energy at a given voltage. The voltage of the capacitor is limited by the diac  54  in this embodiment. The capacitor and diac can be selected to deliver a desired energy pulse and not to deliver an undesirably powerful energy pulse. 
       FIG. 6  shows another exemplary energizing circuit  34   d  comprising a battery  32   d , an oscillator  44   d , an energy storage device comprising an inductor  62 , and an energizing element  19   d  that in this embodiment comprises a firing resistor. The oscillator  44   d , the inductor  62 , and the energizing element  19   d  are connected in parallel with the battery  32   d.    
     The battery  32   d  provides DC current to the oscillator  44   d  which outputs pulses of energy through the inductor  62 . The oscillator acts as a switch that periodically provides a pulse of a desired pulse width. The power output from the oscillator  44   d  charges the inductor  62  which can store energy in a magnetic field. The inductor can discharge the stored energy in a pulse sufficient to activate the energizing element  19   d . In this embodiment, where a 1.5 v battery is utilized as the power source, the inductor  62  can be selected to provide a desired voltage gain based on the windings of the inductor as will be recognized by the skilled artisan. 
     A given inductor can store a finite amount of energy in its magnetic field at which point it reaches “saturation.” Any additional energy is lost as heat rather than being stored in the inductor&#39;s magnetic field. 
     Some of the present embodiments can utilize an inductor that can store a sufficient amount of energy to activate an energizing element, but reaches saturation before enough energy can be stored to potentially damage a given energizing element. Selecting an inductor that reaches saturation when a desired amount of energy is stored in its magnetic field can have a further advantage of allowing the energizing circuit to operate with a wider range of power source voltages. 
     In some of the described embodiments, an activating pulse having a desired voltage level can be achieved by choosing an inductor that can receive energy from the oscillator and create an inductive kickback that produces a higher voltage. Such a configuration can allow relatively low voltage power sources such as a 1.5 v battery to power an energizing circuit that delivers energizing pulses of 40 v or more. 
     For example, in an embodiment employing a 1.5 v AA battery, a brand new battery may supply approximately 1.6 v. The battery may have a lower useful value of approximately 1.0 v before being replaced or recharged. An inductor can be chosen to deliver a desired activating pulse and reach saturation when the battery is at its lower useful range of about 1.0 volts. Thus the inductor stores the maximum amount of energy in its magnetic field and just reaches saturation when supplied with about 1.0 v from the power source. 
     When a fresh battery of about 1.6 v is positioned in the circuit, the inductor stores substantially the same amount of energy as it did when supplied with 1.0 v and thus reduces the chance of the energizing element being damaged from being overcharged. Thus, by choosing a suitable inductor for use with a specific energizing element and battery (power source), a desired activating pulse can be achieved across the effective lifespan of the battery without any other regulation of the energizing circuit. 
     Exemplary Methods 
       FIG. 7  illustrates an exemplary fluid ejecting method. In this implementation, the method charges an energy storage device with oscillating current at  72 . Such an act can allow energy to be stored in the energy storing device. Some implementations can achieve this act by creating oscillating current having a desired frequency. This can be achieved, among other ways, by coupling an oscillator to a DC power source as described above. The oscillator can be chosen based on a desired firing frequency for a given energizing element. For example, firing resistors can be employed as suitable energizing elements. Many firing resistors provide suitable functionality in a fluid ejecting device operating at about 20 to 40 kHz (kilohertz), as described above. Such a frequency can allow for fluid to be replenished in the fluid ejecting device prior to the next pulse. 
     Some suitable implementations can utilize an inductor as a suitable energy storage device. These implementations can store energy inductively in the inductor&#39;s magnetic field. A suitable inductor can be chosen based on the other components comprising a particular implementation. Some of these implementations can prevent damage to the energizing element by selecting an inductor that reaches saturation at or near a value which will deliver a desired pulse thus preventing overcharging and potentially damaging the energizing element. 
     Other suitable implementations can similarly store energy capacitively where a capacitor comprises the energy storage device. The capacitance of the capacitor -at a given voltage can be selected to supply the desired pulse. The capacitor can be utilized in conjunction with an avalanche device that is automatically triggered when a predetermined threshold is met. The predetermined threshold can be the desired voltage of the firing pulse. The avalanche device in combination with the capacitor can store energy defining a desired pulse which can be delivered when the predetermined condition of the avalanche device is met. 
     The method further discharges the energy storage device through an energizing element of a fluid ejecting device sufficient to eject fluid from the fluid ejecting device at  74 . A suitable energy storage device can deliver a pulse of energy of sufficient energy to activate the energizing element while limiting the pulse of energy to reduce the chance of damaging the energizing element. Such a circuit can be achieved by combining components that deliver an energy pulse suitable for a given energizing element. 
     Conclusion 
     The described embodiments can provide methods and systems for simple, relatively inexpensive energizing circuits for activating a fluid ejecting device. The energizing circuits can store energy that is subsequently delivered to a fluid ejecting device&#39;s energizing element sufficient to cause fluid to be ejected. The component of a given energizing circuit can be selected to provide energy pulses sufficient for a given energizing element while limiting the pulse of energy to prevent damage to the energizing element. 
     Although the invention has been described in language specific to structural features and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or steps described. Rather, the specific features and steps are disclosed as forms of implementing the claimed invention.