Abstract:
A handheld inkjet printing mechanism is provided for printing a selected image on a print surface of a solid hard body or a semi-flexible body, such as on human skin for face-painting at carnivals, for temporary tattoos, body decorations and the like, on walls and furniture for printing designs, on packages and building materials for labeling purposes, etc. The printing mechanism has a chassis which supports a controller that stores the selected image. An inkjet printhead supported by the chassis selectively ejects inkjet ink onto the print surface in response to the controller as an operator moves the printing mechanism over the print surface to record the selected image thereon. A printhead-to-print surface spacing device controls the spacing between the printhead and the print surface while printing. A printing method using such a handheld printing mechanism is also provided.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of application Ser. No. 09/428,681 filed on Oct. 27, 1999 now U.S. Pat. No. 6,312,124. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to printing with an inkjet printing mechanism and more particularly to a new handheld, solid and semi-flexible body inkjet printing system for printing images on hard or semi-flexible surfaces, and in particular, on human skin, such as for face-painting at carnivals, for temporary tattoos, for body decorations, and the like. 
     BACKGROUND OF THE INVENTION 
     Typical inkjet printing mechanisms use cartridges, often called “pens,” which shoot drops of liquid colorant, referred to generally page. Each cartridge has a printhead formed with very small nozzles through which the ink drops are fired. Most often, the printhead is held in a carriage that slides back and forth along a guide rod in a “reciprocating printhead” system, with the page being advanced in steps between each pass of the printhead. To print an image on paper media, for instance, the printhead is propelled back and forth across the page, shooting drops of ink in a desired pattern as it moves. Other printing systems, known as “page-wide array” printers, extend the printhead across the entire page in a stationary location and print as the media advances under the printhead. The particular ink ejection mechanism within either type of printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. 
     For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett-Packard Company. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text). 
     To clean and protect the printhead, typically a “service station” mechanism is mounted within the printer chassis so the printhead can be maintained to promote printhead health. For storage, or during non-printing periods, the service stations usually include a capping system which hermetically seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as “spitting,” with the waste ink being collected in a “spittoon” reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead. The wiping action is usually achieved through relative motion of the printhead and wiper, for instance by moving the printhead across the wiper, by moving the wiper across the printhead, or by moving both the printhead and the wiper. 
     To improve the clarity and contrast of the printed image, recent research has focused on improving the ink itself. To provide quicker, more waterfast printing with darker blacks and more vivid colors, pigment-based inks have been developed. These pigment-based inks have a higher solid content than the earlier dye-based inks, which results in a higher optical density for the new inks. Both types of ink dry quickly, which allows inkjet printing mechanisms to form high quality images on readily available and economical plain paper. Typically, these inks are supplied in a reservoir housed by the inkjet cartridge, so when the reservoir is emptied, the entire cartridge including the printhead is replaced in what is known as a “replaceable cartridge” system. Some cartridges are monochrome (single color), for instance, carrying only black ink, while other cartridges are multi-color, typically carrying cyan, magenta and yellow inks. Some printing mechanisms use four monochrome cartridges, while others use a black monochrome cartridge in combination with a tri-color cartridge. 
     Recently, an imaging cartridge system has been introduced by the Hewlett-Packard Company of Palo Alto, Calif., as the DeskJet® 693C model inkjet printer. This is a two-pen printer which uses a tri-color cartridge, carrying full dye-loads of cyan, magenta and yellow, and a black cartridge which may be replaced with a tri-color imaging cartridge. This imaging cartridge carries reduced dye-load concentrations of some colors, such as cyan and magenta, along with a full or partial dye-load concentration of black ink. The imaging cartridge allows the printer to produce more continuous tone changes, particularly flesh tones, so the resulting image has near-photographic quality, with very little graininess. 
     As the inkjet industry investigates new printhead designs, one tendency is toward using a “snapper” reservoir system where permanent or semi-permanent printheads are used and a reservoir carrying a fresh ink supply is snapped into place on the printhead. These snapper reservoirs are typically installed in reciprocating printers, which move both the printhead and the snapper reservoir back and forth across the media for printing. Another new design uses permanent or semi-permanent printheads in what is known in the industry as an “off-axis” printer. In an off-axis system, the printheads carry only a small ink supply reciprocally back and forth across the printzone, with this on-board supply being replenished through tubing that delivers ink from an “off-axis” main reservoir placed at a remote, stationary location within the printer. Rather than purchasing an entire new cartridge which includes a costly new printhead, the consumer buys only a new supply of ink or an “ink bag” for the main reservoir. Typically, the fresh ink supplies are sold individually by color, although in some implementations, a multi-color supply may be furnished. 
     From the discussion above, it is apparent that the vast majority of inkjet printing has been done on paper, although inkjet printing is often done on transparencies, foils, fabrics and other sheet-like media. It would be desirable to provide a new system which expands the concepts of inkjet printing to other uses, such as for printing images on hard or semi-flexible surfaces, and in particular, on human skin, such as for face-painting at carnivals and the like, in a manner that is both easy and economical to use. The matter of permanence, semi-permanence or temporariness of the printed image may be governed, at least in part, by the selection of the ink used to print the image, as well as the environment to which the printed image is exposed. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a inkjet printing system is provided to print an image using inkjet technology on a print media which may be non-sheet-like, such as upon a hard surface, for instance, lumber which is ready to be shipped on a pallet to a jobsite, or on a semi-flexible surface like human skin when face-painting at carnivals, for temporary tattoos, for body decorations, and the like. The printing system includes a handheld inkjet printing mechanism for printing a selected image on a print surface of a solid body or a semi-flexible body. This handheld printing mechanism has a chassis, and a controller supported by the chassis, with the controller storing the selected image. An inkjet printhead is supported by the chassis to selectively eject inkjet ink onto the print surface in response to the controller. A printhead-to-print surface spacing device controls the spacing between the printhead and the print surface. The spacing device is supported by the chassis to traverses over the print surface when moved along the print surface by an operator while the printhead selectively ejects ink onto the print surface to record the selected image thereon. 
     According to yet another aspect of the invention, a method is provided of printing a selected image on a print surface of a solid body or a semi-flexible body, including the step of traversing a chassis supporting an inkjet printhead over the print surface. During the traversing step, in a maintaining step, a selected spacing is maintained between the inkjet printhead and the print surface. In an ejecting step, ink is selectively ejected from the printhead to record the selected image on the print surface during the traversing step. 
     An overall goal of the present invention is to provide an inkjet printing system and method for printing on non-sheet-like material, such as hard or semi-flexible surfaces, such as skin for pace-painting and the like, which is fast, economical, and easy to use, along with providing superior print quality. 
     A further goal of the present invention is to provide an economical inkjet cartridge or replaceable ink supply for use with such a printing system, which is economical and easy for consumers to install, and which prints on and adheres to skin. 
     Another goal of the present invention is to provide a portable, handheld, inkjet printing system which may download images from a computer or scanner, or which may accept image cartridges having one or more images stored thereon, and which may have a display screen to preview the image to be printed, as well as a device which may allow for customization of the image in the field, such as the addition of a name or other information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially schematic, perspective view of one form of a portable, solid body and semi-flexible body inkjet printing mechanism of the present invention, shown here printing an image on a semi-flexible skin surface of an arm. 
     FIG. 2 is a side elevational view of the inkjet printing mechanism of FIG.  1 . 
     FIG. 3 is a bottom plan view of the inkjet printing mechanism of FIG.  1 . 
     FIG. 4 is a partially schematic, perspective view of an alternate form of a portable, solid body and semi-flexible body inkjet printing mechanism of the present invention, shown here coupled to two different image input devices, one being a scanner for loading custom images, and the other being a computer, along with a replaceable inkjet ink supply ready to be installed in the printing mechanism. 
     FIG. 5 is an enlarged side elevational view of the inkjet printing mechanism of FIG. 4, shown ready for installation into storage and printhead servicing mechanism used to maintain printhead health. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-3 illustrate one embodiment of a portable, solid body and semi-flexible body inkjet printing mechanism  20 , constructed in accordance with the present invention, which may be used for printing of information, photographic images, designs, graphics, and the like, such as the moon and stars design  22  on a solid body or a semi-flexible body, such as the skin  24  covering arm  25 , in an industrial, office, home or other environment. This body inkjet printing system may be used in a variety of different portable, hand-held configurations to print images on other surfaces, such as for marking packages in a warehouse, field-marking containers, or pallets of lumber. Many other industrial, business, study and home uses for this portable printer  20  may be envisioned, where a light-weight, portable, easily-read marking system is desired. For convenience the concepts of the present invention are illustrated in the environment of a portable inkjet printer  20  used to form images on the semi-flexible surface of human skin  24 . The print media may be any type of hard or semi-flexible material, but for convenience, the illustrated embodiment is described using skin  24 . 
     While it is apparent that the printer components may vary from model to model, the illustrated inkjet printer  20  includes a first chassis portion comprising a frame or base  26  surrounded by a second chassis portion comprising a housing, casing or enclosure  28 , typically of a plastic material. A group of four rollers or wheels  30 ,  32 ,  34  and  36  are rotationally mounted to the chassis base  26  to move the printer  20  evenly over the print surface, here, skin  24 , in the direction of arrow  38 . The printer  20  also has a printer controller, illustrated schematically as a microprocessor  40 , which in this embodiment receives print instructions from a replaceable, interchangeable image cartridge  42 . The image cartridge  42  is illustrated as being slideably received in a slot  44  defined by the chassis housing  28  to be electrically coupled to the controller  40  when fully inserted in the slot  44 . The cartridge  42  may include a display surface  45  that carries indicia indicating the image or images which may be printed when the cartridge is installed in printer  20 . Preferably, the chassis housing  28  defines a window  46  through which indicia printed on the display surface  45  may be viewed when the cartridge  42  is installed. 
     It is apparent that use of a replaceable image cartridge  42  has many advantages, depending upon the configuration selected for the controller  40 . For example, the main portion of the microprocessor may be housed within the image cartridge  42 , allowing consumers to upgrade the printing abilities of their printer when a new cartridge  42  is purchased. As an alternative to such a “smart cartridge” embodiment, the controller  40  may be constructed to house the main portion of the microprocessor, leaving the cartridge  42  to only carry data to the controller to provide a more expensive printer  20 , and more economically priced image cartridges  42 . Thus, as used herein, the term “printer controller  40 ” encompasses these functions, whether performed by the on-board portion of the controller  40 , by the cartridge  42 , an intermediary device therebetween or linked thereto, or by a combined interaction of such elements. The printer controller  40  may also operate in response to user inputs provided through a key pad  48  or other input device located on the exterior of the chassis casing  28 . 
     In the illustrated example, the skin  24  receives ink from a pair of inkjet cartridges  50  and  52 , which may be monochrome cartridges, such as a black ink cartridge and/or a color ink cartridge. The cartridges  50  and  52  are also often called “pens” by those in the art. The pens  50 ,  52  are received within a receptacle  53  formed within the chassis housing  28  and aligned to the chassis base  26  using conventional datums, for instance as described in U.S. Pat. Nos. 4,872,026 and 5,617,128, both assigned to the Hewlett-Packard Company of Palo Alto, Calif. Multi-color images may be printed using tri-color cartridges, with a black image being formed by printing dots of cyan, magenta and yellow all at the same location, forming what is known in the art as a “process black,” as opposed to a “true black” which would be formed by printing with a black ink cartridge. The pens  50 ,  52  may contain pigment based inks, dye based inks, or other types of inks, such as thermoplastic, wax or paraffin based inks, as well as hybrid or composite inks having both dye and pigment characteristics. 
     The illustrated pens  50 ,  52  each include reservoirs for storing a supply of ink. The pens  50 ,  52  have printheads  54 ,  55  respectively, each of which have an orifice plate with a plurality of nozzles (not shown) formed therethrough in a manner well known to those skilled in the art. The illustrated printheads  54 ,  55  are thermal inkjet printheads, although other types of printheads may be used, such as piezoelectric printheads. The printheads  54 ,  55  typically include a substrate layer having a plurality of resistors which are associated with the nozzles. Upon energizing a selected resistor, a bubble of gas is formed to eject a droplet of ink from the nozzle and onto the print surface, such as skin  24 . The printhead resistors are selectively energized in response to enabling or firing command control signals, which may be delivered by a conventional multi-conductor strip (not shown) from the controller  40  to the printheads, and through conventional electro-mechanical interconnects between the cartridge receptacle  53  defined by the chassis housing  28  and the pens  50 ,  52 , then to the printheads  54 ,  55 . 
     Preferably, the outer surface of the orifice plates of the printheads  54 ,  55  lie in a common printhead plane. This printhead plane may be used as a reference plane for establishing a desired media-to-printhead spacing, which is one important component of print quality. In the illustrated embodiment, the media-to-printhead spacing is determined by the extent to which the wheels  30 - 36  project beyond the lower surface of the printheads  54 ,  55 , as can best be seen in the view of FIG.  2 . Of course there may be some flexibility to the surface of the skin  24 , into which the wheels may protrude, requiring a larger media-to-printhead spacing distance than would be required when printing on a solid surface, such as on lumber or on drywall (also known in the building trades as “sheet rock”). This variance in the print surface characteristics may be accommodated by making the wheels  30 - 36  of a larger diameter for semi-flexible print surfaces like skin, such as by using interchangeable wheels, or by allowing an operator to adjust the wheel height relative to the bottom surface of the housing using a conventional lever or screw mechanism (not shown). 
     As shown in FIG. 1, to track the linear position of the printer  20  as it moves across the skin  24  in the direction of arrow  38 , the printer  20  may include a positional feedback mechanism, such as a conventional rotary encoder  56  which may be mounted to the circular side surface of one of the wheels, for instance on wheel  30 . An optical encoder reader  58  may be mounted to the chassis base  26  to read the indicia on the rotary encoder  56  and provide a positional signal to controller  40 . Such a rotary encoder system  56 ,  58  is known in the art for monitoring media position, such as when a sheet of media advances through the printzone, for instance as described in U.S. Pat. No. 5,774,074. As an operator rolls printer  20  across the skin  24 , the controller  40  coordinates the firing signals sent to the inkjet nozzles of printheads  54 ,  55  with the positional feedback signal received from the encoder reader  58  to direct the ink droplets to print the image  22  according to the instructions on the image cartridge  42 , or according to information stored in the controller  40 . 
     FIGS. 4 and 5 illustrate another embodiment of a portable, solid body and semi-flexible body inkjet printing mechanism  60 , constructed in accordance with the present invention, which may be used for printing of information, photographic images, designs, graphics, and the like, such as the moon and stars design  22 ′, on a solid body or a semi-flexible body, such as the skin  24  covering arm  25 , in an industrial, office, home or other environment. The functions and features of printer  60  are similar to those described above for printer  20 , and both embodiments may be likewise adapted to have similar features. Here we see printer  60  coupled to a host computer  62  from which images, such as design  22 ′ may be downloaded through a signal  64 , which may be hard-wired to the printer at terminal  65 , or may be otherwise downloaded, such as through an infrared or other signal. The design  22 ′ may also be provided to the printer  60  from a scanner  66  through a signal  67 , which may be hard-wired to the printer at terminal  68 , or may be otherwise downloaded, such as through an infrared or other signal. Alternatively, the image  22 ′ may be provided through an image cartridge, as described above for printer  20 . Images to be printed may be downloaded from other sources, such as from the Internet or world-wide web. 
     The printer  60  holds four replaceable ink reservoirs  70 ,  72 ,  74  and  76  which contain black, cyan, magenta and yellow inks, respectively, within receptacles defined by a first chassis portion comprising a main housing or enclosure portion  78  of the printer. The printer  60  has a second chassis portion comprising a printhead housing  80  which is flexibly mounted to the main enclosure  78  at a flexible, gimbal-mounted, neck portion  82 . The chassis main enclosure  78  may be equipped with a display portion  84 , such as an LCD (liquid crystal display) screen that displays usage instructions, or a representation of an image  22 ′ to be printed. Image selection input keys  85  may be used to scroll through a variety of images stored in a controller portion of the printer, which may operate as described above for the controller  40 . Images may be customized through inputs provided by a keyboard, such as an alpha-numeric keyboard  86 . Other input keys  88  may also be provided on the exterior of the chassis housing  78 , such as to begin a print job, or this location may be used to provide an operator with information, such as whether to speed-up or slow down when moving across a print surface, such as skin  24  (FIG.  1 ). 
     The chassis printhead housing  80  holds four inkjet printheads  90 ,  92 ,  94  and  96  which are coupled to the reservoirs  70 ,  72 ,  74  and  76 , respectively, through a series of ink delivery tubes  100 ,  102 ,  104  and  106 , respectively, which extend through the neck portion  82 . While the printheads  90 - 96  are illustrated as being four separate items, as advances in inkjet technology and silicon manufacturing techniques are made, it may be very feasible now, or in the near future to form four large printheads, for instance having nozzles arrays of an inch (2.54 centimeters) or longer, on a single piece of silicon. The ink delivery tubes  100 - 106  may be constructed from a variety of different ink-compatible flexible tubing materials, such as the plastic tubing used in the Hewlett-Packard Company&#39;s DeskJet® 2000C Professional Series inkjet printer. Indeed, the printheads  90 - 96 , as well as the ink reservoirs  70 - 76 , may be constructed using the technology employed in the DeskJet® 2000C Professional Series inkjet printer. 
     To maintain a proper printhead-to-print surface spacing, the printhead housing  82  may include a group of wheels as described above for wheels  30 - 36 , or a group of fixed spacer protrusions or skids  110 ,  112 ,  114  and  116 . The skid bumps  110 - 114  slide over the print surface, such as skin  24 . The chassis printhead housing  80  may also carry an optical sensor  120  which may be used to provide a positional feedback signal to the printer controller, as described above with respect to the encoder  58  of printer  20 , or if equipped with wheels  30 - 36  rather than with the skids  110 - 116 , a rotary encoder may be used, as described above for encoder  56 . Such an optical sensor  120  may be used to view surface irregularities in the print surface such as hairs on the skin, and from this information, determine the speed of the printing stroke  38 . Alternatively, a strip of tape carrying regularly-spaced markings or other indicia may be placed on the print surface to lie under sensor  120  during the print stroke, with the tape acting then as a linear encoder and the sensor  120  acting as an optical pattern sensor to generate a positional feedback signal. 
     As described above in the Background section, inkjet printheads require servicing to maintain pen health. In conventional inkjet printers used to print on sheet media, a service station is typically mounted within the printer housing. For a portable, handheld printer  20  or  60 , to keep the printer unit light weight for ease of use, a separate service station unit  130  is useful. The service station  130  may be constructed in a variety of different ways known to those skilled in the art, for instance, using the principles described in the allowed U.S. patent application Ser. No. 08/667,610, filed on Jul. 3, 1996, and assigned to the Hewlett-Packard Company. The illustrated service station  130  has a receptacle  132  which is sized to receive and grip the chassis printhead housing  80 , as indicated by arrow  134 . The service station  130  has a motor  136  which moves the various servicing components, such as wipers and caps into place to service the printheads  90 - 96 , for instance, in response to inputs received from an operator through a keypad  138 . For instance, a spitting and wiping routine may be required following a print job, followed thereafter by a capping sequence for periods of storage. One of the inputs to keypad  138  may be used to initiate a spitting and wiping routine following a period of storage to ready the printer  20 ,  60  for printing. 
     CONCLUSION 
     A variety of advantages are realized using the handheld inkjet printer  20 ,  60 , beyond the ability to use inkjet technology to print on non-traditional solid body and semi-flexible body print surfaces, as well as on conventional sheet media, such as paper. Preferably, the printers  20 ,  60  are lightweight and portable, for instance about the same size as a man&#39;s electric shaver or a cellular telephone. One advantage of the gimbal-mounted neck  82  of printer  60  is the ability to keep the chassis printhead housing  80  flush with the print surface, allowing for some natural ergonomic tilting of the operator&#39;s hand holding the chassis main body  78  while printing, without inducing drop trajectory print defects in the image  22 . 
     The ability to couple the printer  60  to a computer  62  allows the latest in imaging and photo software to be used to generate images, including customized images, as well as images entered through scanner  66 , for instance the photo of a boyfriend, girlfriend, or one&#39;s favorite pet or hobby. Indeed, the computer  62  may be used to download images from a website on the Internet. The alpha-numeric keypad  48 ,  86  on the printer  20 ,  60  may allow for further customization of images when printing at a location which is remote from a computer, such as when face-painting at a carnival where a child might wish to have their name printed on their skin instead of, or in addition to a design. The alpha-numeric keypad  48 ,  86  may also be useful in other contexts, such as when marking containers during an inventory at a warehouse. Such inventory information could also be stored in the controller  40  of printer  20  or  60 , and later downloaded onto the computer  62 . Indeed, the handheld printers  20 ,  60  may be used to print on other surfaces, such as for applying tole or other designs to furniture or walls, or for addressing packages to eliminate adhesive mailing labels. 
     While the initial thought was to apply a washable ink to the skin for temporary images, in some printing situations, a more permanent ink may be desirable, such as for marking containers in a warehouse. A semi-permanent ink may be desirable for applying an image to the skin instead of a getting a permanent tattoo, with the inkjet image eventually fading away, which may also be useful as a precursor to getting a permanent tattoo to first decide whether one really likes the image selected. Depending upon the type of ink(s) used and the nature of the particular print surface, some preparation of the print surface prior to printing may be desirable, such as wiping skin  24  with an alcohol-soaked pad before printing to assure a clean surface for good ink adhesion. 
     While the illustrated embodiments of printers  20  and  60  both include positional feedback to the controller  40 , using the optical rotary encoder  56  and reader  58  in FIG. 1, and the optical sensor  120  in FIG. 4, positional feedback is not a requirement if an operator has a steady hand with a smooth print stroke, such as in the direction of arrow  38  in FIG.  2 . With a positional feedback system, the display screen  84  may be used to display usage instructions to indicate whether and operator should speed-up or slow down a printing stroke for optimal image quality. It is apparent that a variety of other modifications may be made in implementing the concepts of this invention, as illustrated by the embodiments of printers  20  and  60 , in particular when tailoring these handheld portable printers for particular uses, and the examples discussed above are merely to illustrate a few of the different ways in which such modifications may be made.