JPH0691862A - Print cartridge - Google Patents

Abstract

PURPOSE: To provide a thermal ink jet printing cartridge wherein a pressure adjusting device, an ink filter, an on-demand melting heater, a quick ignition heater and a temp. regulating heater are integrated in a monolithic printing head. CONSTITUTION: Ink 32 changing from a solid phase to a liquid phase is stored in an ink storage part 27. Heat diffusers 33, 35 are heated by an on-demand melting heater 45 to melt the ink. The ink passes through a supply chamber 28 to go toward a printing engine 40. An air bag 30 and a bubble generator 46 perform the reduction of ink or pressure regulation by a temp. change. The pressure regulating device, an ink filter, the on-demand melting heater and a quick ignition heater are incorporated in a monolithic printing cartridge not only to reduce cost but also to simplify assembling.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to thermal ink jet printers, and more particularly to thermal ink jet printheads fabricated on flexible plastic substrates.

[0002]

BACKGROUND OF THE INVENTION Monolithic thermal ink jet printheads typically use flexible plastic substrates for their major structural elements. A droplet generator consisting of a thin film, a barrier, an orifice plate, and electrical connections is incorporated into a plastic substrate. Print cartridges using "hot melt" ink, incorporating a monolithic printhead, pressure regulation, ink filtration, on demand
Melting and rapid ignition heaters must be used. Heretofore, such requirements have been met with the additional use of another component with a monolithic printhead, which adds to the cost of assembly and increases the overall mechanical complexity of the inkjet print cartridge.

A pressure regulator employing a foam generator was developed for thermal ink jet print cartridges using liquid ink and is disclosed in US patent application 07 / 752,107 filed August 29, 1991. Practical devices for bubble generators in liquid ink systems typically include loss of ink due to thermal or height cycles, and internal vacuum during handling of the pen (when the bubble generator is not covered with a layer of liquid). Elaborate branching and pressure compensation to prevent loss. Foam generators are made by molding holes in plastic, punching or stamping holes in metal, and making holes in plastic film. Plastic film foam generators are used as a separate component in liquid thermal inkjet print cartridges and are not integral with the nozzle plate or substrate structure.

It is common practice to use cartridge heaters and other electrical resistance means to generate thermal energy that controls the phase change and temperature of ink jet printers that employ phase change ink. Ink printing mechanisms for phase change inks emit hot liquid ink to prevent loss of ink volatiles or other ink degradation during standby mode and also while the printhead is removed from the printer. In order to prevent this, freezing (solidification) of the ink at the ink droplet ejection orifice is used.

With respect to ink filtration, in many conventional thermal ink jet print cartridges the ink is
It passes through a filter, an ink pipe, and a slot (or hole) in a silicon or glass substrate before entering a droplet generator for ejection. The filter is typically a wire mesh that removes particles that are typically larger than 10-20 microns in diameter. The filter is typically stamped from the plate and inserted into the print cartridge body where it is heat set or swaged in place.

[0006]

OBJECTS OF THE INVENTION In view of the complexity of the thermal ink jet print cartridges described above, it is an object of the present invention to incorporate pressure regulation, ink filtration, on demand melt, and rapid ignition heaters into a monolithic printhead. To further reduce costs and simplify their assembly. It is another object of the present invention to form ink containment, mechanical alignment, and heat transfer features simultaneously with other processing steps to minimize additional processes and obtain additional functionality.

[0007]

SUMMARY OF THE INVENTION The foregoing and other objects are achieved by increasing the level of functional integration (integration) of thermal ink jet print cartridges. The thermal inkjet print cartridge of the present invention contains solid ink /
It is composed of a supply means, a mechanical alignment mechanism for aligning the ink jet cartridge so as to accurately disperse the ink, and a heat diffusion mechanism. Ink containment and alignment is done using a sealed pen body made of plastic or other suitable material. Thermal diffusion is provided by thermally conductive elements located inside the pen body. Pressure regulation is provided by a bubble generator that cooperates with the bellows bladder. The pressure regulation and ink filtration components are incorporated into the substrate containing the print engine.

The print head of the present invention employs a freeze mechanism to fix and seal the bubble generator to maintain the internal pressure below atmospheric pressure inside the ink cartridge. A bellows bladder having an air vent to the outside is provided to keep the partial vacuum relatively constant as the air in the pen body expands or contracts due to heating or cooling.
In addition, the present invention incorporates directly into the structure of the droplet generator,
It has a heater made of the same material and by the same process. The present invention improves upon prior art printhead devices by eliminating the mesh filter and assembly operations by providing individual filters on the plastic substrate for each drop generator or group of drop generators. The aligned holes replace the single through hole of a conventional thermal inkjet printer, which incorporates the functions of ink filtration and ink supply.

Another feature of the present invention is that it utilizes the phase change of hot melt ink to seal the bubble generator when the print cartridge is in standby mode or when the print cartridge is removed from the printer. is there. Removal of the active print cartridge from the printer is delayed until the foam generator orifice solidifies. This removes the local heat source that keeps the ink in a liquid state near the bubble generator and dissipates the heat that melts enough liquid ink to form a fixed plug or skin in or above the bubble generator. By request. This simple mechanism provides ink containment and partial vacuum retention without the need for an extra large number of components and functions as in previous devices.

Another feature of the present invention is the provision of a plurality of heaters and heat spreaders that provide and combine thermal energy to melt the phase change ink on demand for rapid ignition. These two heaters are incorporated into the substrate to form part of the drop generator or print engine. However, on-demand fusion heaters, which can be dispensed with if desired, are usually seen as an integral part of print cartridges. If desired, the pen configuration can be simplified by supplying solid ink to the ink supply chamber where the liquid phase ink resides on demand.
Liquid ink is dispensed to the print engine at a temperature above its melting point to control viscosity. Excessive temperatures above the melting point are used to melt the ink if necessary,
The need for separate on-demand fusing heaters is eliminated, but the dual functions of rapid ignition and temperature control heaters are needed to provide the heat to melt the ink.

[0011]

1 shows a perspective view of a thermal ink jet printer 10 with a carriage 11 that rides on guide rails 12, 13 and is mechanically scanned horizontally as indicated by a first arrow 14. . The horizontal scanning action is controlled in a conventional manner by a computer controlled DC motor (not shown) in association with a single channel linear encoder (not shown) used to close the control loop containing the motor. paper
A print medium such as 15 is provided and can be accordion folding paper or cut sheet paper.
A sheet feeding mechanism (not shown) moves the sheet 15 across the horizontal scanning direction as indicated by the second arrow 16. As the carriage 11 travels across the paper 15, a plurality of ink drops are ejected and a swath 17 of dots of individual dots appears on the paper 15.

FIG. 2 shows a cross-sectional side view of an improved print cartridge 24 that may be used in the carriage 11 of the printer 10 shown in FIG. The print cartridge 24 comprises a hollow airtight container or pen body 25, which may be made of plastic, for example, having a plenum chamber 26, an ink containment reservoir 27, and an ink delivery chamber 28. Bellows air bag
A 30 is installed in the plenum chamber 26 and is mounted inside the top wall of the pen body 25. The ventilation hole 31 serves as a passage from the inside of the bellows air bag 30 to the outside of the pen body 25. As described above, the pen body 25 is composed of an airtight container. The air in plenum chamber 26 typically creates a partial vacuum of between 1 and 4 inches of water. As described below,
The air in the plenum chamber 26 will be heated during operation of the printer 10. The air in the plenum chamber 26 expands when heated. The bellows bladder 30 collapses by the amount that the air expands and provides the stiffness necessary to maintain a partial vacuum in the plenum chamber 26, and thus the expansion of some air trapped in the plenum chamber 26. While maintaining the pressure inside the pen body 25 substantially constant.

The ink containment reservoir 27 contains a fixed amount of solid ink 32. Ink 32 is a phase change ink stored in the form of a solid mass. The ink lump 32 is placed on the upper heat spreader 33, and when the heat spreader 33 is heated, a part of the lower surface of the ink lump 32 that is in contact with the heat spreader 33,
Liquefaction the same way a hot iron plate melts a mass of butter. The upper heat spreader 33 is made of a metal that is a good heat conductor, such as aluminum or copper. A heat insulator 34 is installed between the upper heat spreader 33 and the lower heat spreader 35. The lower heat spreader 35 is also made of aluminum and is installed below the thermal insulator 34 to keep the ink 32 in the ink supply chamber 28 liquid. Thermal insulator 34 can be made from any conventional non-thermal conductor. The upper and lower heat spreaders 33, 35 and the heat insulator 34 are fixed to the inner wall of the pen body 25 by a suitable connecting means. The on-demand melting heater 45 is installed physically close to the end of the upper heat spreader 33. The rapid ignition and distribution temperature control heater 44 is in thermal contact with the lower heat spreader 35.
The on-demand melt heater 45 heats the ink 32 to a temperature above its melting point and causes it to flow into the delivery chamber 28. The heater 44 heats the ink in the ink feed chamber 28 to 10 to 40 ° C. higher than its melting point to obtain the low viscosity required for ejection.

The use of phase change inks typically requires two independent heat sources, a demand fusion heat source and a rapid ignition heat source. Phase change inks can degrade when subjected to excessive melt / freeze cycles or after long storage in the liquid state. For this reason, it is desirable to melt the liquid phase in an amount necessary to replenish it immediately after it has been consumed by droplet ejection. For example, about 5 watts is needed to heat a solid ink from room temperature to a supply temperature with phase change in a printhead with 100 nozzles ejecting 75 picoliter droplets at 4 KHz at 50% duty cycle. Time average input is required.

Being able to bring the phase change inkjet printer 10 online quickly from a cold starting point is a significant advantage to the user. To do this, the rapid ignition heater 44
Is provided to melt the ink contained in the ink supply chamber 28. As will be described below, a bubble generator 46, or a pressure regulator comprising a bubble generator orifice 46 and a bellows bladder 30, is used to maintain the plenum chamber 26 at a partial vacuum. It is advantageous to place the bubble generator 46 near the rapid ignition heater 44. Starting from room temperature, operating temperature is reached in 10 seconds, and pressure regulation typically requires at least 33 watts per milliliter of molten ink. Typically, temperature sensor 122 (FIGS. 3 and 9) is located in ink delivery chamber 28 and is connected to the temperature control loop shown in FIG.

A flexible, typically L-shaped, folded print engine 40 consisting of a plastic substrate 41 is disposed on one side of the pen body 25 and around the bottom surface. An adhesive (not shown) provides structural attachment and sealing between the print engine 40 and the pen body 25. The rapid ignition heater 44 and the demand fusion heater 45 are installed on the inner surface of the plastic substrate 41 (adjacent to the pen body 25) and perform both the demand fusion and the rapid ignition functions. These heaters have the same materials and process steps used for non-passivated inkjet heaters and conductors.
Can be used for 4, 45.

A novel feature of the present invention is that means for supplying thermal energy to melt the phase change ink on demand and for rapid ignition is incorporated into the drop generator or substrate 41 forming the print engine 40. This eliminates the need for additional components and assembly steps in making the thermal inkjet cartridge 24.

A separate on-demand fusing heater 45 can be dispensed with if desired, but this heater is commonly seen as an integral part of print cartridge 24. If desired, the pen configuration can be simplified by supplying solid ink on demand to the ink delivery chamber 28 where liquid phase ink is present. The liquid ink is dispensed to the print engine 40 at a temperature well above its melting point (eg 10-30 ° C.) to control viscosity. Excess temperatures above the melting point can be used to melt the ink if desired without the use of another on-demand melt heater 45, but a rapid ignition and dispense temperature control heater to provide the heat of melting. You need 44.

The upper heat spreader 33 becomes hot when the on-demand fusion heater 45 is activated by supplying it with power. As the temperature rises above the melting point of the solid ink mass 32, in the portion in contact with the upper heat spreader 33,
A phase change of the ink 32 occurs. The liquid then flows by gravity through holes 36, 37, 38 (shown more clearly in FIG. 3) of upper heat spreader 33, insulator 34, and lower heat spreader 35, respectively. The liquid has a rapid ignition heater 44
And enters the distribution chamber 28, which is controlled by the lower heat spreader 35.

The pen body 25 is provided with a large opening 43 on its side surface adjacent to the melting heater 45 when required. Ink is supplied to the pen body 25 from the ink supply chamber 28 to the print engine.
At least one small opening 42 feeding into 40 is provided. Flexible fold print engine 40 is a fully integrated monolithic thermal inkjet drop generator mechanism. The flexible fold print engine 40 is constructed on a flexible substrate 41, which can be made of plastic such as polyimide or the like. The bubble generator 46 is associated with the bellows bladder 30 to regulate the ink dispensing pressure. The bubble generator 46 is formed by providing a laser ablation orifice 46 (or a collection of orifices 46) on a plastic substrate 41. The diameter of the orifice 46 is typically
150 to 250 microns, depending on the surface tension of the liquid at the dispense temperature.

The bubble generator 46 operates as follows. The pressure at which air begins to bubble into the liquid is known as an orifice 46
Measuring by is well known to those skilled in the art of measuring the surface tension of liquids exposed to its vapor. This principle is used in the present invention to adjust the ink distribution pressure.
The meniscus of the bubble generator orifice 46 is drawn into the ink containment reservoir 27 at a pressure below atmospheric pressure. A partial vacuum is created as ink is drawn from the reservoir 27 and ejected by the drop generator or print engine 40. Bubbles can enter the ink supply chamber 28 due to the destruction of the meniscus. The additional volume of air introduced in this manner is proportional to the time average of the air entering through the bubble generator 46, which balances the volume of ink drawn for printing, maintaining the plenum chamber 26 at a substantially constant pressure. It becomes a means of adjustment. The bubble generator 46 provides a source of air that creates the volume that is expelled. The foam generator 46 acts like a valve with a predetermined opening (or "cracking") pressure. Foam generator 46
Does not allow air to enter the plenum chamber 26 unless the plenum vacuum is high enough to break the meniscus.

The pressure at which the meniscus collapses and the bubbles are drawn is determined by the diameter of the bubble generator orifice 46, the surface tension of the liquid ink 32, and the wetting angle of the liquid ink 32 with respect to the material of which the bubble generator 46 is made. For nominal values of surface tension and wetting angle, the adjusting pressure is the bubble generator orifice.
Set by selecting a diameter of 46. Orifice
The smaller the 46, the higher the partial vacuum created. The partial vacuum is typically measured by the height (in inches) of the water column that the vacuum can support. Reducing the diameter of the orifice 46 (by causing air to bubble in the ink delivery chamber 28) increases the partial vacuum in which the adjustment is made.
For example, in a phase change ink application having a surface tension of 24 dynes / cm, a 160 micron diameter orifice 46
Adjust to 2.5 inches of water (measured in the plane of foam generator 46).

The present invention incorporates a pressure regulator integral with the substrate 41 forming the bubble generator or print engine 40, thereby requiring the addition of additional components and assembly steps during the fabrication of the thermal inkjet print cartridge 24. It shows a new feature that it does not exist. In addition, the regulator has a local heat source (rapid ignition heater 44) that liquefies the ink that is solid in the ink chamber 28 so that bubbles can enter the liquid phase, and local heating during handling and shipping. A means of removing the source (switching off the rapid ignition heater 44) to seal the bubble generator orifice 46, preserving the partial vacuum in the pen body 25, and preventing ink ejection is used.

The preferred embodiment incorporating the foam generator 46 in the plastic substrate 41 can be enhanced by a simple external dust shield (not shown) of plastic or other suitable material. Placing the foam generator 46 on the exposed flat surface of the print cartridge 24 makes it susceptible to paper dust and other contaminants that affect the wettability of the outer surface. This can affect the pressure regulation and, in the worst case, can cause ink to drip from the bubble generator 46 and the drop ejection orifice.

The air in the plenum chamber 26 is heated by the heater 4
The pressure regulation by the bubble generator 46 operates in conjunction with the bellows bladder 30, as the pressure changes due to the significant temperature changes as 4, 45 are activated. The air in the plenum chamber 26 is
It is in a partial vacuum state of 1 to 4 inches of water adjusted by the bubble generator 46, but expands when heated by the melting heater 45 on demand. At constant pressure, the volume of air in plenum chamber 26 expands approximately 1/3 when heated from room temperature to 120 ° C. The bellows bladder 30 has the rigidity necessary to maintain a partial vacuum in the plenum chamber 26 and collapses by the amount that the air expands, which can significantly expand the air trapped in the plenum chamber 26. While possible, the pressure remains almost constant. In the present invention, the volume change is substantially due to the heat generated inside the bellows air bag 30.
Is about 40% of the total volume of the plenum chamber 26, which compensates for air expansion when the solid mass 32 of ink is nearly exhausted. Bellows bladder 30
Can also be accomplished by other suitable means, such as an elastomeric bladder or a piston utilizing a substantially constant preload.

Another inventor employed by the assignee of the present invention considers a flexible plastic substrate as a structural element of a thermal inkjet printhead. Others have variously integrated thin films, barriers, orifice plates, and electrical connections on flexible plastic substrates. The present invention provides an improvement over prior art inkjet printheads by incorporating three additional features: pressure regulation, ink filtration, and rapid ignition and on demand melt heaters. Combined with conventional components, these features, with the exception of the ink containment, mechanical alignment, heat transfer, and volume compensation components, provide a plastic substrate 41.
A complete thermal inkjet print engine 40 can be built on top of.

FIG. 3 is a cutaway cutaway view of a print cartridge 24 made in accordance with the principles of the present invention. FIG. 3 illustrates the method of assembling the cartridge 24 and the relative positions and relationships of its components. In particular, FIG. 3 illustrates how the on-demand melting heater 45 contacts the outer end of the upper heat spreader 33 and the rapid ignition heater 44 contacts the underside of the lower heat spreader 35. In this way, a heat path is created between one of the heaters 44, 45 and the corresponding one of the heat spreaders 33, 35. The holes 36, 37, 38 and the ink delivery chamber 28 are more clearly illustrated, but these are the liquefied inks.
Reference numeral 32 denotes a path that passes along the way to the print engine 40.

FIG. 4 illustrates one embodiment of the highly integrated monolithic print engine 40 of the present invention. FIG. 4 is a plan view of the front side of the substrate 41 before bending. The substrate 41 has, for example, high tensile strength, dimensional stability, and chemical inertness to ink. Made from plastic, like polyimide. The bending line 50 is formed by laser ablation of continuous punched holes, and the substrate 41 on the right side of the bending line 50 is formed.
This portion forms an orifice plate 51. A plurality of droplet discharge chambers 52 are formed by laser ablation to a depth of about half the thickness of the substrate 41. Droplet ejection chambers 52 are separated from each other by an unablated portion of substrate 41 that defines a built-in ink barrier. Each droplet discharge chamber 52 is provided with a nozzle 53 that penetrates through the substrate 41 and is completely ablated. The nozzle 53 has a predetermined diameter and ejects a small drop of liquid ink 39 from the cartridge 24 onto the paper 15. Five chambers 52 and 53 are shown in FIG. 4 for convenience, but in practice there may be more or less. Droplet ejection chambers 52 can be photolithographically formed in a thin film material, such as a solder mask material, laminated on substrate 41 and orifice plate 51 without affecting the key features of the invention. it can.

A plurality of vaporization heaters 54 for vaporizing the ink in the droplet discharge chamber 52 are provided to the left of the folding line 50.
The vaporization heater 54 can be formed by a well-known thin film process or thick film process. It will be appreciated that the orifice plate 51 is folded at the fold line 50 before the droplet ejection chamber 52 is overlaid on the heater 54. Ink supply room for ink 32
The small opening 42 that feeds from the 28 to the droplet discharge chamber 52 has a vaporization heater 54.
It is provided near the. A plurality of conductive lines 55 forming a flexible circuit individually connect the vaporization heater 54 to an electric connection terminal 56 provided at the left end of the substrate 41. A common return circuit line 64 connects all or a group of vaporization heaters 54 to a common return circuit terminal 65. The bubble generator orifice 46 is completely ablated through the substrate 41 near the vaporization heater 54.

FIG. 5 is a plan view of the back side of the substrate 41. It will be appreciated that after the print engine 40 is folded around one side and the bottom of the pen body 25 as shown in FIG. 2, the back side of the substrate 41 shown in FIG. In FIG. 5, the first broken line (indication line 50)
Is along the fold line 50 forming the orifice plate 51. The second dashed line 61 defines an L-shaped fold line that separates the side surface 57 of the substrate 41 from the bottom surface 58. Nozzle 53 is an orifice plate
Ablated ink delivery opening 42 visible in 51
Can be seen near the lower surface 58 of the substrate 41. The bubble generator orifice 46 can be seen in the bottom surface 58 of the substrate 41. The rapid ignition heater 44 is installed on the bottom surface 58 of the substrate 41 and includes a conductive line 60 extending to the via 61b. The on-demand fusion heater 45 is installed on the side 57 of the substrate 41, and the via 63
Another conductive line 62 extending to b is provided. The common return circuit line 66 is the rapid ignition heater 44 and the demand fusion heater 45.
To the common return circuit via 67b.

FIG. 6 is a perspective view of the print engine 40 bent into an L shape. In this figure, the droplet generator is formed by bending the orifice plate 51 along the laser ablation perforation at the fold line 50 and overlapping the droplet discharge chamber 52 with the vaporization chamber 54.

Rapid ignition heater 44 and on-demand fusion heater
45 may be thin film heaters formed by a metal layer on the backside of the substrate 41 shown in FIG. 5, or alternatively, those heaters already have heaters 44, 45 in place on the substrate 41. It can be formed by laminating plastic films. There are several options for the configuration of the rapid ignition heater 44 and the on-demand fusion heater 45. The heaters 44, 45 are typically 0. with conductors on each end.
It may consist of a thin film resistor made of a resistor material with a resistance of 5 to 3 square. Other embodiments employ the same configuration with openings in the resistor material. This electrically isolates the heater from the jumper that connects the front conductor with a plated through hole. The currents that crowd around these terrains produce non-uniform heating. This can be neglected or minimized by spatially arranging the vias. Another embodiment places a resistive strip between the edge conductors. The space between the strips is used to electrically isolate the heaters 44, 45 from the jumpers between the front conductors. This configuration can also be used to provide multiple squares of resistive material to control the overall resistance of the heater.

There is yet another option for the rapid ignition heater 44. A foam generator 46 is installed inside the heater 44 to meet the need to rapidly melt ink on the foam generator 46 and in the ink feeder 28 between the print engine 40 and the plenum chamber 26. be able to. The heater material can be directly exposed to the phase change ink 32 to efficiently transfer heat without the thermal resistance of the intervening layer. Optionally a foam generator
The heater material may need to be removed to control the wetting angle near 46. Another embodiment forms the rapid ignition heater 44 from a thick film that can be applied by silk screen printing or other suitable means. This heater 44
Like the thin film heater 44 previously described, the conductors 60, 66 and
Make electrical connection with 62.

In another embodiment, the heaters 44 and 45 are replaced by the thin film heater 4
It is formed on another plastic substrate using a different process than that used for 4, 45 and the conductors are formed on the front side as shown in FIG. These heaters 44, 45 and conductors do not require the accuracy of lithographic printing of the front side metallization, and the cost of separating both the back side heater and conductor steps from the stage used for the folded substrate 41 of the present invention. There are advantages. Then vaporize the plastic substrate with heaters 44, 45 and conductors 60, 66, 62
54, the droplet ejection chamber 52, the orifice 46, etc. can be stacked on the substrate. With the second membrane and heater window openings in the manner described above, the bubble generator 46 can be formed in the outer plastic layer by a laser ablation process and bubbled through the stacked layers. The laminated heater makes electrical connection with conductors 60, 62, and 66 as previously described. The connection can be by soldering, conductive epoxy, or other suitable means.

Conventional thermal inkjet print cartridges use ink filters that consist of woven wire mesh. Typically, the wire mesh is selected to exclude particles larger than 10-20 microns in diameter to prevent clogging of the droplet ejection orifice. The present invention uses laser ablation to form the array of filter holes 70 in the plastic substrate 41, as shown in FIG. This is done at the same time as the ablation of the droplet ejection chamber 52, firing nozzle 53, and other structural features including the foam generator orifice 46.

FIG. 7 is an enlarged front view of the integrated print engine of FIG. 3, showing in particular the details of an integrated ink filter made with an array of filter holes. The illustration shows filter holes 70 each having a diameter of typically 10-20 microns.
3 shows details of an integrated ink filter formed by the arrangement of FIG. The footprint 71 of the droplet ejection chamber 52 after folding can be seen as a dotted line surrounding the array of filter holes 70 and the vaporization heater 54. A round hole 70 is shown, but other configurations,
Ovals, ovals, and slots are also useful. A sufficient number of holes 70 are needed so that the impedance of the flow through the integrated filter is within acceptable limits even if some holes 70 are plugged. The number, diameter, and shape of the holes 70 can be selected to obtain a nominal replenishment impedance for fluid matching of the drop ejection chamber 52. It should be understood that these filter holes 70 are used in place of the small ink delivery openings 42 shown in FIGS. 2, 4 and 5. It should also be appreciated that the array of filter holes 70 can be used in phase change ink pens as well as liquid ink pens. Therefore, another novelty of the present invention resides in an ink filtration system integrated on substrate 41 and forming a droplet generator 46,
This eliminates the need for additional components and assembly steps when manufacturing thermal inkjet print cartridge 24.

Referring now to FIG. 8a, a cutaway cross-sectional view of drop generator 40 is shown. Solid particles in the ink reservoir 91
There is a wall 92 containing the liquid ink 32 containing 93. The bent portion 94 of the substrate 41 has a filter hole 70 for separating the liquid ink 32 from the droplet discharge chamber 52 and the discharge nozzle 97.
There is an array of. In operation, the array of filter holes 70 is a solid particle
Make sure 93 does not enter the drop ejection chamber 52. Liquid ink 32
Can also be a liquid of phase change ink. Now Figure 8b
8a, there is shown a cross-sectional view of the droplet generator of FIG. 8a. The bent portion 94 of the substrate 41 is provided with a filter hole 70 leading to the droplet discharge chamber 52. As can be seen from FIG. 8b, a vaporization heater 98 is provided on one wall of the droplet ejection chamber 52 formed of the substrate 41, and an ejection nozzle 97 is provided on the opposite wall.

Referring now to FIG. 9, a schematic diagram of a control system 110 for regulating temperature and ink level in thermal inkjet print cartridge 24 is shown.
A solid mass of phase change ink 32 is contained in the ink containment reservoir 27 and liquid ink 115 is present in the ink delivery chamber 28.
The solid mass of the phase change ink 32 is placed on the upper heat spreader 33. The demand melting heater 45 is schematically illustrated by a resistor, and is connected to a demand melting ink level adjuster 120 which is connected to a power source 121 to obtain electric power. An ink level sensor 122 is provided on the wall of the pen body 25 near the ink feed chamber 28 to maintain the liquid dispensed to the print engine 40 at an appropriate level. The ink level sensor 122 is electrically connected to the ink level adjuster 120, and this combination controls the amount of heat generated by the on-demand melting heater 45. The ink level adjuster 120 compares the signal from the ink level sensor 122 with a predetermined value representing the nominal ink level. Upon receiving a signal that is less than the nominal ink level in the ink delivery chamber 28, the on-demand melt heater 45 is energized to melt the solid ink 32. The liquid entering the ink delivery chamber 28 raises the ink level and power is removed from the on-demand melt heater 45 when the ink level sensor 122 indicates a level above the nominal value. Ink level sensor 122 can use any number of means known to those of skill in the art. This includes a thermistor that operates in a self-heating mode and the liquid that is present absorbs heat from the device and reduces its temperature below that observed in the presence of the liquid.

The rapid ignition heater 44 is shown schematically as a resistor and is incorporated into the print engine 40 and electrically connected to the distribution temperature regulator 124. Distribution temperature controller 1
24 also draws power from power supply 121. The temperature sensor 125 is installed in the ink supply chamber 28, where the temperature of the liquid ink 32 can be monitored. The temperature sensor 125 is electrically connected to the distribution temperature controller 124, which combination controls the amount of heat generated by the rapid ignition heater 44. The regulator 124 compares the temperature related signal from the temperature sensor 125 with a predetermined internal reference value. Power is applied to the rapid ignition heater 44 whenever the temperature sensed by the temperature sensor 125 is below a predetermined value. Temperature sensing means well known to those skilled in the art, such as thermistors, thermocouples, and temperature sensitive resistors can be employed as the temperature sensor 125. A simple control algorithm utilizing proportional, integral, and derivative compensation, or a combination thereof, may be used for both the ink level regulator 120 and the dispense temperature regulator 124.

[0040]

As described above, pressure adjustment, ink filtration,
A new and improved integrated monolithic thermal inkjet printhead incorporating on-demand (on-demand) fusion heaters and rapid ignition heaters is provided. While the disclosed features are useful for solid phase change ink printheads, the array of filter holes is also useful for liquid ink print cartridges. Adopting a local heat source to liquefy the solid ink so that the bubbles from the bubble generator pressure regulator can enter the liquid phase, remove the local heat source during handling and shipping to seal the bubble generator orifice, It is one feature of the present invention to preserve the partial vacuum in the regulator and prevent ink ejection. Another feature is that the expansion of the air in the plenum chamber due to the internal heat generation is compensated by the bellows that vent to the outside. It should be understood that the above-described embodiments are merely illustrative of some of the many specific embodiments that demonstrate application of the principles of the invention. Obviously, those skilled in the art can easily devise numerous other configurations without departing from the scope of the invention.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a thermal inkjet printer.

FIG. 2 is a side sectional view of the print cartridge of the present invention.

FIG. 3 is a partially exploded perspective view of the print cartridge of the invention.

FIG. 4 is a plan view of a print engine used in the print cartridge of FIG.

5 is a rear view of the print engine of FIG.

FIG. 6 is a perspective view of the print engine of FIG. 4 which is L-shaped for mounting.

FIG. 7 is a partially enlarged view of the print engine of FIG.

FIG. 8a is a partially enlarged view of the ink drop generator.

8b is a sectional view taken along line 8b-8b in FIG. 8a.

FIG. 9 illustrates a control system for a solid ink print cartridge.

[Explanation of symbols]

10: thermal inkjet printer, 12, 13: stick, 15: paper,
24: print cartridge, 25: pen body, 26: plenum chamber, 27: ink storage unit, 28: ink feed chamber, 3
0: Air bag, 32: Solid ink, 33, 35: Heat diffuser, 36, 3
7, 38: Passage, 44, 45: Heater, 46: Bubble generator, 40: Engine, 34: Thermal insulator, 41: Substrate,

Claims (1)

[Claims] 1. A function of phase change ink volume and enclosure temperature in a thermal inkjet printhead having a plenum chamber, a flexible substrate having a terrain defining a liquid ink ejection chamber, an orifice plate, and a plurality of heating elements. A print cartridge having pressure adjusting means arranged in the housing so as to change its volume, and a bubble generator arranged in the flexible substrate.