MXPA96005882A

MXPA96005882A - Detection system to detect the presence of an ink container and its level of it

Info

Publication number: MXPA96005882A
Application number: MXPA/A/1996/005882A
Authority: MX
Inventors: Carlotta Michael; J Dietl Steven; W Altfather Kenneth; M Stevens Donald; F Hubble Fred Iii
Original assignee: Xerox Corporation
Priority date: 1995-12-14
Filing date: 1996-11-27
Publication date: 1997-08-01

Abstract

A detection system for detecting the presence of an ink container and its ink level, characterized in that it comprises: first means for directing light operatively connected to the container, a first light source having output beams directed towards the means for directing light when in a mode for container detection, means of photodetectors for detecting the presence or absence of directed light of the means directing light and for generating an output signal indicative thereof, second means for directing light operatively connected to the container, a second light source having output beams directed towards the second means for directing light when in low ink level detection mode and photodetector means, for detecting light directed from the second means for directing light, the level of detected light and therefore the level of photodetector output signal, representative of the presence or absence of and ink adjacent to the outer surface of the second means for directing the

Description

DETECTION SYSTEM FOR DETECTING THE PRESENCE OF AN INK CONTAINER AND SD INK LEVEL BACKGROUND AND DECLARATION OF MATERIAL DESCRIPTION The present invention relates to ink jet recording devices and more particularly to a system for detecting the presence of a container. of ink supply and also to detect when the ink level in the container is at or below a predetermined level. Ink-jet recording devices eject ink onto a printing medium such as paper, in controlled patterns of closely spaced points. To form color images, multiple arrays of ink jets are employed, with each group being supplied with ink of a different color from an associated ink container. Thermal inkjet printing systems use thermal energy selectively produced by resistors located in full capillary ink channels near orifices or channel termination nozzles to momentarily vaporize the ink and bubble on demand. Each time bubble ejects a droplet of ink and moves it to a recording medium. The printing system can be incorporated either in a cart type printer or a type printer across the page. A REF: 23235 cart type printer generally has a relatively small print head that contains the nozzles and ink channels. The print head is usually sealingly connected to an ink supply container and the combined print head and container form a reciprocating cartridge assembly to print a piece of information at a time on a stationary recording medium, such as paper. After a section is printed, on paper a distance equal to the height of the printed section is stepwise advanced, so that the next printed section will be contiguous. The procedure is repeated until the entire page is printed. In contrast, the printer across the page has a stationary printhead that has a length equal to or greater than the width of the paper. The paper moves continuously beyond the page-width printhead, in a direction normal to the print head length at a constant speed during the printing process. Inkjet printers type * mobile carriage should either transport the ink container together with the print head or provide a flexible ink supply line or line, and between the mobile print head and a stationary ink container. The page width printers have an ink supply container located outside the printing area and connected directly to the ink channels in the print bar. Whether for a printhead with partial width of a moving carriage or for a print bar across the page, it is convenient to have a low ink level warning to signal a user to replace or replenish the container of ink, so that the ink does not run out during a print job. Currently for some applications (such as graphics), some users choose to install new printing containers before starting an extensive print job because it is less expensive to replace a questionable container instead of losing one or more colors in the product prints. It is also important to ensure that the ink supply container is in the proper location; for example, fluidly connected with the associated printhead. In some cases, a spent ink container may be removed but a replacement container may be neglected. Operation of the printer with the container removed may potentially damage the associated print head. Various methods and devices of the prior art are known to detect reduced levels of ink in an ink supply container. The patent of the U.S.A. No. 4No. 342,042 discloses an ink detection system, including output from an LED detector, reflected from a flexible membrane that serves as the upper surface of a reservoir for ink supply. The membrane shrinks as one ink level becomes exhausted, and the LED detector senses shrinkage and generates a low ink level signal. The patent of the U.S.A. No. 5,079,570 provides a method for detecting ink levels in an ink cartridge, wherein the ink is supplied from a foam container. A binary fluidic indicator is fluidly coupled to the foam container and triggers when the fluid level in the foam reaches a certain predetermined level. The patent of the U.S.A. No. 5,289,211 discloses a low ink content detection system that includes a pair of electrodes immersed in the foam reservoir impregnated with ink. The electrodes are connected to a bridge circuit that measures the electrical resistance of the ink between the two electrodes. The patent of the U.S.A. No. 5,414,452 employs a logic circuit that counts the number of drops ejected and compares the present number with the maximum number of drops equivalent to a known value of ink in the ink tank. The patent of the U.S.A. No. 5,434,603 describes a visual indicator system wherein the side walls of the reservoir are withdrawn inward during depletion of ink by changing the orientation of indicator strips and modifying the visible color to an observer through the window. The patent of the U.S.A. No. 5,386,224 places a probe for level detection in the ink supply and detects changes in electrical conductivity of the ink. The patent of the U.S.A. No. 5,136,305 discloses a low ink content detection system, wherein a thermostat is placed in the ink supply and energized periodically. The temperature increase of the ink is measured and compared with pre-set values to determine the ink depletion state of the deposit. The patent of the U.S.A. No. 4,639,738 discloses a detection system that incorporates detection gates in the cartridge, to detect pressure conditions in the top and bottom of the cartridge. The gates are coupled to a pressure differential detector that signals a replenishment condition. Japanese publication No. 5-332812 discloses a low ink level detection system, wherein the cartridge has a transparent optical path member installed in an opening in a surface of an ink storage tank. An LED emits a beam of light that is guided to the ink tank and reflected back to a detector to provide an indication of low ink levels.

Some of the references of the prior art are relatively expensive based on measurement and detection of ink conductivity or circuitry for fall detection. In addition, none of the references of the prior art include means for ensuring that the ink tank is in proper position, before starting the ink level detection operation. BRIEF DESCRIPTION OF THE INVENTION Therefore, an object of the present invention is to provide a detection system that confirms the proper installation of an ink container that supplies ink to an associated print head. Another objective is to present a detection system, to detect a low level of ink in the ink container and to provide a low ink level warning signal. Another object of the invention is to provide an ink supply container that is constructed "to permit an economical optical detection system, which performs both the ink container detection and the low ink level detection function. invention, and in an exemplary embodiment, a thermal printer is described, including a printhead for printing on a recording medium in response to image pulse signals.The ink is supplied to the print head from an ink container which is fluidly connected to the printhead.The print head and container are mounted on a scanning carriage which moves in both directions through a printing area, the print head ejecting droplets of ink from nozzles to form a image in the middle of recorded an optical system comprises two sources of light and a light detector is located fixedly on the path of and travel of the carriage and positioned in such a way that the light from the light source is directed to the ink container as it is placed opposite the optical system. The ink container has elements for directing optical light formed in a transmitting wall. The light from the light sources is directed in and on the container through the transparent wall and sequentially on the optical elements. In one embodiment, the elements that direct light are reflecting prisms; Light reflections of these elements or the lack thereof, are detected by a common photodetector, to provide signals representing the presence or absence of the container and the level of ink remaining in the container. More particularly, the present invention relates to a detection system for the presence of an ink container and the ink level there, comprising: first light directing means operatively connected to the container, a first light source having beams of output directed towards the means for directing light, when in a mode for detection, of container, means of photodetectors for detecting the presence or absence of light directed to the means for directing light and for generating an indicative output signal, seconds means for directing light operatively connected to the container, a second light source having output beams and directed towards the second means for directing light when in a mode for low ink level detection and photodetector means for detecting directed light from the second means to direct light, the level of light detected and therefore the level of the photodetector output is repr representative of the presence or absence of ink adjacent to the interior surface of the second means for directing light. In addition, the present invention relates to a method for detecting the presence or absence of a cartridge mounted on a mobile carriage and employed in an inkjet printer and the level of ink in an ink container associated with the cartridge, which includes the steps of: directing a light beam at an optical detection station, moving the carriage at the optical detection station such that a portion of the cartridge, if present, intercepts the light beam, detect the presence or absence of light sent to another direction from the portion and generate a signal representative of the presence or absence of a cartridge. The invention also relates to a system for detecting the presence or absence of an ink cartridge in an ink recording device, the cartridge includes a print head and an ink container for supplying ink to the print head, the system includes: at least one print head for printing each of a first color on a recording medium, an associated ink supply container for providing ink of the first color to the print head, the container having at least a partially transparent section of a wall, the wall has at least one associated reflecting member, means for moving the cartridge over a scanning path, an optical detection station located on the scanning path and comprising a light source and a photodetector, means for moving the cartridge inside the station, such that if the cartridge is physically present, the reflecting member is opposite to the light source outlet and means for energizing the light source, the photodetector either detects a light source output beam reflected from the reflecting member, thereby indicating the presence of a cartridge or detecting the lack of reflected light, which indicates the absence of a cartridge. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates a perspective view of an inkjet printer incorporating the ink container and a low ink level detection system of the present invention. FIGURE 2 is a cross-sectional view through the ink cartridge illustrated in FIGURE 1, FIGURE 3 is an algorithm used to sequence checks to determine presence or absence of a container as well as ink level inside the container . FIGURE 4 is a block diagram of the control circuitry for controlling operation of the detection system. FIGURE 5A is a cross section of a prism-shaped reflective element within the cartridge showing the prism container with a sufficient level of ink.

FIGURE 5B is a cross section of the prism of FIGURE 5A showing the reflection path in a low ink environment. FIGURE 6 is a graph of output signals that detect low ink level against volume of ink exhausted in the cartridge. FIGURE 7 illustrates a perspective view of a full-color inkjet printer incorporating the ink containers and the low ink level detection system of the present invention. FIGURE 8 is an algorithm for the embodiment of FIGURE 7, which is used to sequence the presence or absence of a container and detection of low ink level sequentially. FIGURE 9 is an alternative embodiment of a cartridge detection system incorporating a pipe or light tube. FIGURE 10 is an alternate embodiment of the optical assembly illustrated in FIGURES 1 and 2. DESCRIPTION OF THE INVENTION FIGURE 1 illustrates a perspective view of a thermal inkjet printer 8, incorporating a preferred embodiment of the ink container and the low level ink detection system of the present invention. The printer 8 is only exemplary. The invention can be practiced in other types of thermal inkjet printers as well as other reproducing devices such as piezoelectric printers, dot matrix printers and inkjet printers directed by signals from a Scanner with Document Scanning Feed. The printer 8 includes a cartridge with an ink jet print head 10 mounted on a carriage 12, supported by carriage rails 14. The carriage rails are supported by a frame 15 of the ink jet printer 8. The cartridge print head 10 includes a container 16 shown in detail in FIGURE 2, which contains ink for supplying a thermal ink jet printing head 18, which selectively ejects ink droplets under control of electrical signals received from a controller 50 ( FIGURE 4) of the printer 8 through an electric cable 20. The container 16 comprises a housing 17 having a wall 17A that seats reflective elements 21 and 22, illustrated in greater detail in FIGURE 2. The container 16 is fluidly connected However, it can be replaced when the ink runs out, alternatively, the entire cartridge can be replaced at each exhaustion, depending on the particular requirements of the system. The print head 18 contains a plurality of ink channels that convey ink from the container 16 to holes or nozzles for ejecting ink. When printing, the reciprocating carriage 12 in both directions on the carriage rails 14 in the direction of the arrow 23, the full width path constitutes a scanning path. The current printing area is contained within the scan path. As the printhead cartridge 10 reciprocates in both directions on a printing path and past a recording medium 24, such as a sheet of paper or a transparency, ink droplets are ejected from selected nozzles of the print head towards the sheet of paper. Typically, during each step of the carriage 12, the recording medium 24 is held stationary. At the end of each step, the recording medium 24 is advanced stepwise in the direction of the arrow 26. For a more detailed explanation of the operation of the printer 8, reference is made herein to US Pat. No. 4,571,599, and US Pat. No. of Re-expedition 32,572, which are hereby incorporated by reference. Also FIGURE 1 is illustrated an optical sensing assembly 30. With reference to FIGURES 1 and 2, the assembly 30- includes a housing 31 into which a first light source 34, a second light source 36 and a second light source 36 are mounted. a photodetector 38 located between two sources of light and commonly used as will be seen. The light sources are electrically connected to a power source while the output of the photodetector 38 is electrically connected to the system's control circuits as will be seen, the container 16, in a preferred embodiment, is designed as a two compartment unit. The assembly 30 is placed in the carriage path, such that as the wall of the receptacle housing 17A moves to a position opposite to the mounting 30, the light of the light source 34 is directed towards the light steering element 21, and the light from the light source 36 is directed towards the light direction element 22. The photodetector 38 is positioned to detect the light directed either from the element 21 or the element 22 in the manner described in more detail to continuation. FIGURE 2 includes a sectional view of the print head cartridge 10 on line 2-2 of FIGURE 1 and shows the housing 17 and the print head 18 connected to the container. The print head 18 is connected fluidly but in detached form to the container 16. The housing 17 is made of a lightweight but durable plastic, which in a preferred embodiment is polypropylene. The housing 17 has an air inlet 32 and an ink outlet 34 formed within the wall 17B. The air inlet 32 allows an air transfer between the interior of the housing 17 and the environment. The ink outlet 34 provides fluid transfer from the ink contained in the ink container 16 from the interior of the housing 17 to the ink jet print head 18. The manifold 37 directs the filtered ink from the ink outlet 34 to the print head 18 and the ink ejection orifices, for ejecting ink on the recording medium 24. The housing 17 defines an interior space divided within a first chamber 40 and a second chamber 42 by a partition member 44. The partition member 44 extends from a side wall of the housing 17 to an opposite side wall in the housing and essentially divides the housing into the first chamber 40 and the second chamber 42, such that the second chamber 42 is larger than the chamber 42. first chamber 40. The first chamber 40 contains an ink retention member 46 typically made of foam material to hold or retain liquid ink. The liquid ink 48, stored in the second chamber 42, is transferred from the second chamber 42, which is substantially free of an ink retention material, to the ink retention material 46 through an ink inlet 41 defined by the ink. division member 44. A fill gate 49 allows the cartridge to be filled with ink. The ink 48 passes the ink retention material 46 through the ink inlet 41 and the ink is released through the ink outlet 34 as necessary to supply the print head 18 with printing ink. In order to maintain an appropriate amount of ink in the ink retaining material 46 for supplying the print head 18, the housing 17 includes a mechanism for transferring ink from the second chamber 42 to the first chamber 40 by maintaining an adequate amount of pressure of the ink. air over the liquid ink 48, to fill the material 46 with ink when necessary. This mechanism includes a steering member 60, which defines with the split member 44, a passage for air transfer 62 having an inlet for ventilation 64 coupled to a vent outlet 66 for pressurizing the second chamber 42 to a condition static (without flowing). The steering member 60 does not extend from a side wall to an opposite side wall as the partition member 44, but instead forms a vent pipe. The construction of the compartments of the container 16 as described herein is exemplary. There are other known ways to build an ink supply container with dividing sections, while maintaining an appropriate counter pressure to the print head nozzle. See, for example, the container described in U.S. Pat. No. 5,138,332 and in the co-pending application Serial No. (D / 94372), both of which are incorporated by reference. For purposes of the present invention, it is understood that the container is constructed such that during operation, the ink moves from the chamber 42 to the chamber 40 through the passage between the two compartments under established pressure conditions by well-known techniques. by those with skill in the specialty. Of interest for the present invention is the modification made to the ink container 16 by introducing the prism member 21 and ceiling mirror 22 to the wall 17A defining the rear of the chamber 42. With reference particularly to FIGURE 2, in FIG. a preferred embodiment, the light steering element 21, is a reflector formed integrally in the lower half of the wall 17A and made of the same light transmitting material as the wall; for example polypropylene, in a preferred embodiment. Polypropylene or other hydrophilic materials are preferred. The prism is constructed with faceted surfaces 21A, 2IB, which extend into the interior of the compartment 48 and at an angle to each other at an angle of approximately 82 °. The prism has a truncated pyramidal shape with surfaces 21A, 21B connected by facet surface 21C. The prism can be constructed of multiple narrow facet sections to avoid the commonly encountered manifold when injection molded-large sections and also provide improved pipes for light. The light steering element 22 is also formed as part of the wall 17A. In the preferred embodiment, the element 22 is a prism having two facet surfaces 22A, 22B, extending into the interior of the compartment 48 and at an angle to each other connected by the surface 22C. The element 22 is formed in a ceiling mirror by placing films, thin sheets or reflective tapes 22D, 22E on the surfaces 22A, 22B, respectively. It will be appreciated from the foregoing that only a portion of the wall 17A needs to be transmitter; for example, the portion that accommodates the reflective element .21. Further, while the preferred embodiment has reflective elements constructed integrally within the wall of the housing, the elements can be placed separately adjacent to the interior surface of the wall 17A. OPERATION PB SYSTEM DETECTION PE The detection system of the present invention which is considered to comprise the combination of reflective elements 21, 22 and optical assembly 30, is designed to be activated to perform a low level ink check and presence of ink container that follows specific events such as the start of a print job or after printing a certain number of prints. To perform the checks, the printer follows an algorithm that requires the ink container to be placed adjacent to the assembly 30 and then sequenced through a series of detection steps. FIGURE 3 is a modality of an algorithm that can be used. FIGURE 4 shows control circuitry for implementing the ink container and the system for ink level detection. A main controller 50 conventionally includes a UPC, a ROM, for storing complete programs and a RAM. The controller 50 regulates the carriage movement 12 as well as other printer functions described below. When a line registration operation is performed, each resistor associated with a jet in the print head 18, is selectively moved according to the image data from a personal computer P / C 52 or another data source sent to the controller 50. The controller 50 sends impulse signals to the heater resistors of the print head, causing droplets of ink to be ejected from the jets associated with the heated resistor, thereby forming a registration line on the surface of the recording medium. With continuous operation of the print head, the ink contained in the chamber 42 of the container 16 is gradually exhausted until a level which has been predetermined to constitute a low ink level is reached. For purposes of description, the detection system will be considered as active, first at the beginning of a print job, and at a later time, following a predetermined period of operation of the printer. OPERATION AT THE START OF THE PRINT JOB Referring to FIGURES 1-4, image signals from the P / C 52 to the controller 50, initiate a print start sequence. The carriage 12 moves to the detection station 41, to place the receiving wall 17A of the adjacent container 16 and facing the optical assembly 30. Under the command of the controller 50, an energy source 56 first energizes the light source 36. The source 36, in a preferred embodiment, is an LED with a peak wavelength in the range of 880 to 940 nm. A beam of light is directed towards the housing wall 17A, and if a container is present, the light is reflected from the reflecting surfaces 22D, 22E, of the ceiling mirror 22 and sent to another direction so that it impinges on the photodetector 38. The two reflections allow the beam to be staggered vertically downwards to avoid an angle of incidence higher than that acceptable in the detector. The output signal of the photodetector 38 is sent to the logic circuitry within the controller 50 which determines that the signal is within a predetermined range. The controller then sequencing to energize the second light source 34. If a container 16 is not present, the light output from the source 36 will not be reflected back to the photodetector 38. The lack of photodetector output will be recognized in the computer as a state of "missing container." The printer will be disabled, and a warning display will be activated on Display P / C 55 informing the user that a) color printing associated with the missing tank will be avoided and b) the correct container it must be installed to avoid potential damage to the printhead.

In a preferred embodiment, the light source 34 is also an LED with characteristics similar to the source 36. The source 34 emits a light beam that is transmitted through the wall 17A and is incident on the face 21A of the prism 21. FIGURE 5A is a cross section of the prism 21 and a schematic reproduction of the assembly 30 showing the path of the light beam when the prism is still immersed in ink and therefore the ink level exceeds a predetermined low level. The low level ink detection is activated by applying the principle of total internal reflection. The total internal reflection occurs when a ray, which passes from a higher refractive index to a lower one (from N to N '), has an angle of incidence whose sine is equal to or exceeds N' / N. The critical angle L, is expressed by the equation: lc = arc sinus N '/ N (1) As illustrated in FIGURE 5A, the output beam of the LED 34 passes through the wall 17A, which being polypropylene and with a refractive index of approximately 1492, is almost completely transparent to light, allowing it to pass through approximately 96% of the incident light and be incident on the facet surface 21A at an approximate angle of 45 *. Since the back side of the surface 21A is immersed in ink with an approximate refractive index of 1.33, and the critical angle is not reached, approximately 99% of the incident light will be transmitted to the ink and at a refractive angle of approximately 51.4 ° and they are approximately < 1% will be reflected to face 21B. Since the inner facing side of the face 21B is also immersed in ink, > 99% of 1% will also be transmitted to the ink. Only a very small amount (approximately 0.01%) of the original incident energy will be reflected back to the photodetector 38. The output signal of the photodetector in the controller 50 will register a low light level that falls outside a predetermined low ink density range. established in the memory of the controller. The controller will compare this signal with a prior status signal to determine if a container, previously identified as in a low ink content situation, has been replaced or replenished. A status register, or readjustment, is then established at a "non-empty" level, and the impulse circuit of the print head 61 in the controller 60 is activated to send impulse signals to the print head to initiate a sequence of impression. The low ink level threshold for this mode has been set to 20% of the container fill level 16. To summarize the operation of the detection system so far, the presence of an ink container is confirmed. Furthermore, it has been confirmed that the ink inside the container is above predetermined levels, and therefore, a printing job can be started. The ink level detection system operation will now be described at a second time set for it to occur after some predetermined operational time. OPERATION DURING PRINT JOB As the printer 8 begins to print a print job corresponding to the image feed signals of the P / C 52; Ink is removed from the compartment foam 40 (FIGURE 2) thereby reducing the saturation of the foam. A flow path is created which allows the ink in the compartment 42 to replenish the foam. In this way, the ink level of the compartment 42 falls off gradually during use of the printer. A low level ink check can be started at the end of each print job or after some predetermined number of pixels, for example 7 X 106 pixels printed for any color since the last check. For purposes of illustration, a print job will be considered to have concluded upon lowering the ink level in the compartment 42, to a point below a predetermined trigger point level represented by the dotted line 80. A method of detecting Low ink level starts at this point. Continuous printing is interrupted and as previously described, the carriage 12 moves to a position such that the receiving wall 17A and the prism 21 are opposite to the detection assembly 30. The new sequence controller via energization of light sources 34, 36 (the detection of the container may be omitted). FIGURE 5B shows the effect of the low ink level in the light beam. Light from source 34 passes through wall 17A, and is incident at facet 21A at approximately 45 °. Since the ink level has dropped below the 20% fill level, the ink is no longer in contact with the back surface of facet 21A, which is now exposed to the air with a refractive index of l.o. The critical angle of 42.9 ° is exceeded by the incident light in the facet; therefore, none of the incident light is transmitted through the surface. The rays are fully reflected back to the denser medium which results in a total internal reflex (TIR) of the beam. All incident energy is reflected towards facet 21B. Since the back of this facet is also exposed to air, all energy is now directed back to the photodetector 38. Approximately 92% of the incident energy (minus any absorption) is returned to impinge on the photodetector 38. The signal The output of the photodetector is recognized by the control logic as being within a range of low preset or predetermined ink level. The controller performs a status check to see if the change from a previous station status is from "not empty" to "empty". Since this is the case for the present example, the status register memory in the controller 50 is set to "empty" state and a low ink level signal is generated and displayed in a P / C 55 display. The signal The low ink content can be used, depending on the system requirements, to simply display a low ink level to an operator, to stop the printing operation until a refill or cartridge replacement is performed or, in the preferred embodiment, to allow the operation to continue, but with a modified "low ink level" status. As illustrated in FIGURES 3 and 4, the controller sends a signal to P / C 52, which exhibits an appropriate warning by defining the ink container that has just been verified to be low in ink. Each ink container contains a remaining amount of ink that can be correlated with a number of remaining pixels (or droplets). This number may be different for each ink color. The low ink content signal generated in the logic of the controller allows the counter 60 to start counting the number of pixels (drops) ejected from the "print head" jets and the ink reduction within the ink tank. pre-set of pixels has been counted, the ink tank is defined as exhausted and the printing is automatically deactivated.The termination occurs before the tank runs out completely (approximately 2-5% level) in order to ensure that the head The printhead and its ink channel lines are not emptied, a condition that would impair the reliability of the printhead.During the time between the first detection of low ink content and declaration of ink depletion, increasingly urgent messages may be displayed on the printhead. the P / C display, it is understood that the pixel value of the remaining ink depends on the frequency of the low ink content checks. Rior presents a condition wherein the prism 21 is either completely immersed in ink or completely free of ink. Between these two cases is a transition represented by a light level monotonically increased to the signal of the LED 34, as the ink level gradually exposes more and more of the facet 21A to the air. FIGURE 6 shows a stroke or ink plot, in milliliters (mi), supplied to the printhead against detector output signals in volts. For the first 70% of ink supplied, the detector current is low, and the voltage output through a comparison circuit in the controller 50 is high. Between 70 and 75% depletion, a rapid transition occurs as the output beam of the LED 34 begins to be fully reflected internally from the facets 21A and 21B of the prism 21, thereby increasing the output current from the detector 38 and causing a rapid voltage drop in the circuit.

The invention can be used in other types of inkjet printing systems, including full-color printers. FIGURE 7 shows a type of printer color scan. With reference to FIGURE 7, a thermal inkjet printer 70 is illustrated. Various ink supply cartridges 72, 73, 74, 75, each with an integrally connected thermal print head 76 to 79, are mounted in a sliding carriage 77. During the printing mode, the carriage 77 reciprocates in both directions on the guide rails 78, in the direction of the arrow 81. A recording medium 80, such as for example paper, is held stationary while the The carriage moves in one direction and before the carriage moves in a reverse direction, the recording medium is stepwise advanced by a distance equal to the height of the data strip printed on the recording medium by the thermal print heads. Each print head has a linear array of nozzles that are disposed in a direction perpendicular to the reciprocating direction of the carriage. The thermal printheads drive the ink droplets 82 towards the recording medium when droplets are required, during the travel of the carriage to print information. Flat cables carrying signals connected to terminals of the print head have been omitted for clarity. The printer 70 can print in multiple colors, wherein each cartridge 72 or 75 contains a different color ink supply. For a representative color printer and additional control details, see for example U.S. Pat. No. 4,833,491, the description of which is incorporated herein by reference. According to the invention, each of the ink containers forming part of the cartridges 72-75, is of the same construction as the cartridge illustrated in FIGURE 2, and for the purpose of the invention, each cartridge has a container of ink that has two prism reflectors formed in the wall facing outwards. One reflector is associated with the presence detection of cartridge and the other with detection of low ink content. The cartridge 72 is illustrated to have an ink container 80 with reflective members 82, 84. The cartridges 73-75 have similar containers and reflective members not specifically required for ease of description. As in the single cartridge mode, a detection assembly 90 includes a housing 92 within which a first light source 94 and a second light source 96 and a photodetector 98 located between the two light sources are mounted. In operation and with reference to FIGURES 4, 7 and 8, image signals from the P / C 52 to the controller 50, initiate a printing principle sequence. The carriage 77 moves in order to place the cartridge 72 with the first ink container 80 opposite the detection assembly 90. Under the controller 50, the power source 54 is caused to sequentially energize the light sources 94, 96, while that the output of the photodetector 98 is measured. The sequencing and detection operation for the cartridge 72 is the same as previously described for the cartridge 10. The source 96 is first energized to verify that the cartridge is present (reflections of the ceiling mirror 84 to the photodetector are within the range), the source 94 is turned on and the ink level in the container system is determined after making comparisons with the previous state. (Reflections from the front surface of the prism 82 are perceived by the photodetector 98). Once the cartridge 72 is serviced, the carriage 77 moves to place the next cartridge 73 in the position to be detected. The preceding process is activated for each cartridge until it has been confirmed that all cartridges are in place and all ink levels in the mounting ink containers are either within acceptable levels or appropriate low ink level warnings are They have exhibited in the P / C. -While the modality described here is preferred, it will be appreciated from this teaching that various modifications, variations or alternate improvements can be made by those with skill in the specialty. For example, detection of the presence or absence of the ink container can be achieved by using other elements to direct light. An example is a light tube illustrated in FIGURE 9. FIGURE 9 shows a portion of a container 16 'with an optical element 22' placed on the outside of the receiving wall 17A '. The element 22 'is a curved light tube in order to send the light to another direction which enters the end 22'A and which comes out at the end 22'B to the photodetector 38'. The optical element 22 'can alternatively be an optical fiber. With any embodiment, the same function as the reflective element 22 is performed in Figure 2. If the container is present, a high current is generated in the photodetector 38 '. The modes of light transmission may be preferred for some systems since the reflective thin strip or sheet used to form the ceiling mirror 22 for the embodiment of FIGURE 2 may not adhere well to the prism facet surfaces. And while the optical assembly 30 of the embodiment of FIGURE 1 is considered optimal, other arrays of the light sources and photodetectors of the assembly consistent with the invention are possible. An example is illustrated in FIGURE 10, which employs a light source and two photodetectors. As illustrated, an optical assembly 100 includes first and second photodetectors 102, 104, and whose output signal is read by the controller. An LED light source 106 is connected to a power source. The operation to detect the container is the same as the preceding description. The light level will be detected in the photodetector 104 with an appropriate signal that is sent to the controller. Correspondingly, the low ink content reading is made in the detector 102. In this mode, the LED can either be operated continuously or intermittently (pulsed). Another less efficient arrangement is possible (not shown) where a light source and detector are associated with each reflective element 21, 22 in FIGURES 1 and 2. As another example, while the modalities of FIGURE 1 and FIGURE 7 show the ink container mounted on a scanning carriage which is periodically moved to a detection station, the ink containers can be placed in a fixed location and connected to the scanning print head, by means of a flexible ink supply line. For the embodiment of FIGURE 1, the container 16 will be fixed in an opposite position to the optical assembly 30 and connected to the print head 18 by means of a flexible tube. For the embodiment of FIGURE 7, four optical assemblies will be located outside the opposing printing area of an associated ink container, each of the ink containers connected to the respective print head cartridge by flexible ink couplings. In the case of a full-width printing head of the type described, for example, in US Pat. No. 5,221,397, a remote ink container is connected to an ink manifold that connects ink with the plurality of feed modules that butt-fit together to form the full width assembly. One or more optical assemblies will be located opposite the modified ink container. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims

CLAIMS 1. Ui detection system for detecting the presence of an ink container and its ink level, characterized in that it comprises: first means for directing light operatively connected to the container, a first light source having output beams directed towards the means for directing light when in a mode for container detection, photodetector means for detecting the presence or absence of directed light from the directing means and for generating an output signal indicative of the second, second means for directing light operatively connected to the container, a second light source having output beams directed towards the second means for directing light when in low ink level detection mode and photodetector means, for detecting the light directed from the second means for directing light, the detected light level and therefore the level of photodetector output signal, representative of the presence or au ink supply adjacent to the outer surface of the second means for directing light. The detection system according to claim 1, characterized in that the first means for directing light comprise a ceiling mirror. 3. The detection system according to claim 1, characterized in that the second means for directing light comprise a prism with a plurality of facets. 4. The detection system according to claim 3, characterized in that the prism is constructed of a plurality of multiple narrow facet sections. 5. The detection system according to claim 1, characterized in that the photodetector means detect in a common and sequential way reflected light from both the first and second means for directing light. The detection system according to claim 1, characterized in that the first and second means for directing light are formed integrally in a container wall. The detection system according to claim 3, characterized in that the container is filled with ink to a depth that covers at least the prism, causing the light incident on the prism facets to be almost completely transmitted to the ink resulting in a low amount of light reflected to the photodetector or photosensor, the photodetector or photosensor generates a signal indicative of an ink level above a predetermined low level. The detection system according to claim 3, characterized in that the light is completely reflected internally on the prism facets when the ink level falls below the prism, resulting in an increased amount of light that is reflected at the photodetector, the photodetector generates a low ink level signal. The detection system according to claim 1, characterized in that the first means for directing light comprise a light tube. A system for detecting the presence of an ink container, characterized in that it comprises: means for directing light operatively connected to the container, a light source having output beams directed towards the means for directing light when they are in a mode for container detection and photodetector means for detecting the presence or absence of light from the means for directing light and for generating an output signal indicative thereof. 11. The detection system according to claim 10, characterized in that the means for directing them comprise a reflecting member. The detection system according to claim 10, characterized in that the means for directing them comprises a light tube. The detection system according to claim 10, characterized in that the support for the means for directing light is integrally formed in a container wall. 14. The detection system according to claim 13, characterized in that the container has a wall with at least a portion of the wall that is transparent and wherein the reflecting means is located inside the container, whereby the light beams of the light source are directed on the member reflecting through the transmitting portion of the wall of the container. 15. The system according to claim 11, characterized in that the reflective means is a ceiling mirror. 16. A system for detecting the presence or absence of an ink cartridge in an ink recording device, the cartridge includes a print head and an ink container for supplying ink to the print head, the system is characterized in that it includes : at least one print head for printing each of a first color on a recording medium, an associated ink supply container, for providing ink of the first color to the print head, the container has at least a partially transparent section of a wall, the wall has at least one reflective member associated therewith, means for moving the cartridge over a scanning path, an optical detection station located on the scanning path and comprising a light source and a photodetector, means to move the cartridge to the station, such that if the cartridge is physically present, the reflective member is either placed at the exit of the light source and means for energizing the light source, the photodetector either detects an output beam of light source reflected from the reflecting medium, thereby indicating the presence of a cartridge or detecting the lack of Reflected light indicating the absence of a cartridge. 17. The system according to claim 16, characterized in that it also includes optical means mounted below the reflecting means, the cartridge detection station further comprises a second light source aligned to direct a beam of light against the optical means, the means that energize the light source sequentially energize the light source with the photodetector that generates signals representing the presence or absence of a cartridge followed sequentially by an ink level signal, the optical media, when covered with ink, provide a high ink level signal, and when exposed to air, provide a low ink level signal. 18. A method for detecting the presence or absence of a cartridge mounted on a mobile carriage and used in an inkjet printer, characterized in that it includes the steps of: directing a light beam in an optical detection station, moving the carriage in an optical detection station, such that a portion of the cartridge, if present, intercepts the light beam, detects the presence or absence of light sends back from said portion and generates a signal representative of the presence or absence of a cartridge. The method according to claim 18, characterized in that the directed light is sent to another direction from a reflecting portion of the cartridge. The method according to claim 18, characterized in that the directed light is transmitted back from a transmission portion of the cartridge. 21. An ink supply container, characterized in that it comprises: a housing defining an interior space and having an air outlet located in a first position and an ink outlet located in a second position, at least one container wall is at least partially constructed of a light transmitting material, and a reflector formed integrally within the transparent wall and having at least two reflective facet surfaces extending away from the wall and into the interior of the housing and at an angle to each other. 22. The ink cartridge according to claim 21, further comprising a second reflector integrally formed within the wall and having at least two light transmitting facet surfaces extending away from the wall and into the interior of the housing., the transmitting surfaces are at an angle to each other. 23. A device for detecting a cartridge, for detecting the presence of an ink cartridge in an ink printer, characterized in that it comprises: an ink container having a reflective element installed in a container wall, a light emitting source for emit light on a path intercepted by the reflective element and a detector to sense the presence of reflected light from the reflective element and to generate an output signal representative of the detection. 24. A detection system for detecting the presence of an ink container and the ink level, characterized in that it comprises: first means for directing light operatively connected to the container, a light source having output beams directed towards the first means for directing light when in a container detection mode, first photodetector means, for detecting the presence "or absence of light directed from the means for directing light and for generating an output signal indicative thereof, second means for directing light operatively connected to the container, the light source has output beams directed towards the second means for directing light when in a mode for detecting low ink level and second photodetector means, for detecting light directed from the second means for directing light , the detectable light level and therefore the photodetector output level are representative of the presence or absence of ink adjacent to the interior surface of the second means for directing light. 25. A system for detecting ink, for verifying the level of ink in an ink container from which the ink is gradually removed, characterized in that it comprises: a multi-faceted prism placed in the container so as to be initially covered by the ink contained there, but to be discovered gradually as the ink is removed from the container, a source of light having output beams directed towards the prism and incidents in the facets, the light is almost completely transmitted to the ink when the prism is covered by the ink and it is reflected in a completely internal way on the facets of the prism when the prism is discovered, a photodetector placed in order to detect the light reflected from the prism, the photodetector generates a low ink output signal, when the light is detected fully reflected internally, means for verifying the amount of ink that is removed after generation of the low ink level detection signal and means for defining an exhausted ink state for a container. 26. The system in accordance with the claim 25, characterized in that the ink container supplies ink to a print head of an ink recording device and wherein the ink verification means includes counter means for counting the number of drops ejected from the print head and for generating a indicative output thereof and logical means for verifying the output of the counter means and for deactivating the recording device when a pre-set number of drops has been counted by the counter means. RESOLUTION OF THE INVENTION The present invention relates to a system for detecting low content of ink combined with a system for detecting an ink cartridge, to allow an inkjet printer to be more efficient. An ink container that supplies ink to an associated print head is modified by the incorporation of two elements to direct light, in the preferred embodiment, a faceted prism and a ceiling mirror, inside a transparent wall of the container housing . The cartridge, comprising the ink container and the associated print head, is mounted on a scanning carriage. Periodically, the car is transported to a detection station comprising a pair of light source and a commonly used photodetector. A first light source is energized and a beam of light is directed to a place where the ceiling mirror would be placed if the cartridge is present. If the cartridge is absent, the lack of a reflected return signal is detected, indicating that a cartridge has not been inserted. The print operation is stopped until a cartridge is inserted. If a cartridge is inserted properly, the ceiling mirror returns most of the incident light to the photodetector that creates a signal indicating the presence of the cartridge. A second light source is then energized and directed towards the faceted prism, which is either immersed in ink or exposed to the air inside the container. In the latter case, the light is reflected internally by the prism facets back to the photodetector. If a printing operation is in progress, and the ink level has dropped, the common photodetector detects either a strong or weak light component sent to another direction and initiates a status check and generates appropriate displays of low ink level or ink warnings exhausted.