System and method for drying ink on a printing medium

Abstract: A system and method is provided for drying ink deposited onto an printing medium (12) by a printer. The printer includes therewithin primary heat generating modules (126,30) which generate excess heat within the printer when the ink is printed onto the printing medium (12), a thermally conductive platen (22) over which the printing medium moves within the printer during the printing of the ink onto the printing medium (12), and heat conductive contacts (24). It also includes heat conductive contacts for conductively attaching the primary heat generating modules (26,30) to the thermally conductive platen (22). The primary heat generating modules are conductively attached to the thermally conductive platen through heat conductive contacts. The primary heat generating modules (26,30) generate excess heat for conductively heating the thermally conductive platen. Then, the printing medium is moved into contact with the heated thermally conductive platen (22) thereby heating the printing medium (12). Next, the printing ink is deposited by the printer onto the heated printing medium. The ink on the heated printing medium is dried by effects of the elevated temperature imparted to the printing medium (12) by the heated thermally conductive platen (22). In this way, faster printing throughput and improved print quality are provided.

Description: This invention relates generally to the concept of drying ink applied to a printing medium by a printer during its printing operation, and more particularly to the drying of the ink without using the use of dedicated heaters for that purpose. Prior art printer dry ink imprinted into a printing medium, usually paper, through the use of heaters. These heaters do nothing else but dry the ink. Typical conventional methods of removing heat from a printer employ the use of dedicated heat sinks. For example, U.S. 4,982,207 to Tunmore et al. refers to a platen heater system for providing heat to a print sheet during its dwell time on the platen. The platen system comprises a heat foil for heat transfer between a power source and platen through a platen shell. U.S. 5,046,420 to Sondergeld et al. describes a printer for tempering the operating temperature of printer elements by means including diversion of hot air generated by a printer to the elements to be tempered. It is stated that the printer avoids the potential need to heat application from an external source (col. 2, lines 19-26). U.S. 3,074,332 to Robinson refers to a drying platen adapted for heat transfer relationships with a record. The platen is heated by "insert heaters". U.S. 3,170,393 to Reinke describes a heat settable ink curable by brief engagement with a heated surface after imprinting. U.S. 3,934,112 to Lakhani discloses a heater platen with electric heater elements for volatilizing a liquid toner carrier after imaging. U.S. 4, 751, 528, U.S. 4, 951, 067 and U.S. 5,043,741, all to Spehrley, Jr., refer to heat-controlled platens for use in conjunction with hot melt ink. In US-A- 5, 136,329 there is disclosed a printer comprising a thermally conductive platen and a heat generating module in contact with the platen. Heat generated in the heat generating module is conductively transferred to the platen, thereby heating the platen. Printed media contact with and travel across the platen and are provided with heat which causes ink on the printed media to dry. This invention is directed to a system and method for drying ink on a printing medium during the printing process, and to a printer which employs such system and method. Instead of removing heat from a printer using a dedicated heat sink, as is done in some prior art systems, the subject system has created a non-dedicated heat sink therewith in by conducting heat from a printer power supply to a thermally conductive platen for drying ink imprinted on paper in contact with the thermally conductive platen and thereby dissipating the heat from within the system. For liquid-based printing processes, e.g., ink jet printing, the heated platen aids the ink drying process, allowing for faster printing throughput and improved print quality. The introduction into the subject system of conventional dedicated heat sinks is not required again avoiding additional costs and additional space within the printer. This also allows for increased product density due to the space availability. Paper moving over the thermally conductive platen automatically helps to remove heat build up within the printer whenever it is used. The heat removal rate is automatically matched to the rate of heat generation in the system. In accordance with the present invention there is provided a method for drying ink deposited onto a printing medium and a printer for carrying out the method as specified in claims 1 and 6 hereinafter. Typically, the primary generating modules comprise a power supply or a motor. The thermally conductive clips preferably comprise metal clips and the thermally conductive platen is preferably made of a good metallic thermal conductor material. As for the printer, it is typically a liquid-based printer and preferably an ink jet printer. Preferably, the thermally conductive platen includes means for drying the ink printed on the printing medium thereby providing for faster printing throughput and improved printed quality. More specifically, in the printer of the present invention, the thermally conductive platen acts as a non-dedicated heat sink. By employing this system and method, the excess heat generated is dissipated by moving the printing medium over the thermally conductive platen. The excess heat is conducted away from the thermally conductive platen through the movement of a corresponding amount of the moving printing medium, the moving printing medium improving air convection cooling over the thermally conductive platen. As for the printer, it is typically a liquid-based printer, and preferably an ink jet printer. The heat conductive contacts preferably comprise metal clips. Preferably, the thermally conductive platen includes means for drying the ink printed on the printing medium thereby providing for faster printing throughput and improved print quality. As for the printer, it is typically a liquid-based printer, preferably an ink jet printer. FIG. 1 is a schematic perspective view of a system for removing excess heat from a printer for printing ink onto a printing medium. FIG. 2 is a schematic side view of the system of the present invention. FIG. 3 is a schematic end view of the system of the present invention. FIG. 4 is an enlarged detailed view of a specific component being heat sinked by a thermally conductive platen. Referring now to FIG. 1, a system "10" for drying printing ink deposited onto a printing medium 12, typically paper, by a printer (not shown). The printer is employed for printing ink onto a printing medium. The system 10 can be used in any printer. However, it is particularly useful in the GEM printer, a small portable printer manufactured by Hewlett-Packard Company. The printing medium, which is typically paper 12, is moved through the printer by a rotating shaft 14 driven by an electric motor 16. The shaft and motor have respective intermeshing gears 18 and 20. Thus, gear 18 on shaft 14 is driven by gear 20 disposed on and driven by motor 16. Gear 18, and in turn shaft 14, are driven in a clockwise rotational direction by gear 20, which in turn is driven by motor 16 in a counter clockwise rotational direction. As paper medium 12 is transferred through the printer it moves over a platen 22, typically a thermally conductive platen, during the printing of the ink on to the printing medium. The thermally conductive platen 22 is rectangular in shape and is typically constructed from a good thermal conductor, particularly a good metallic thermal conductor such as copper or the like. The thermally conductive platen 22 is heated as described below, and the heated platen is used to dry the printing ink on the paper 12. As best shown in FIGS. 2-4, heat conductive metal clips 24 are attached to the underside of thermally conductive platen 22. The purpose of these clips is to hold the components which are to be heat sinked by thermally conductive platen 22 in heat conductive contact therewith. Thus, transistor 30, which generates excessive heat during use, is held in heat conducted contact by metal clips 24 to thermally conductive platen 22 (see FIG. 4) Transistor 30 is powered by a printed circuit board 26 and is electrically connected to board 26 by wires 28. In use, the primary the heat generating modules, transistor 30 and power supply 26, respectively, are conductively attached to thermally conductive platen 22 through heat conducted contacts, i.e., metal clips 24. Heat is generated within the printer whenever it needs to print. As the printer is printing and generating heat, paper 12 feeds over the thermally conductive platen 22 which also acts as a heat sink drying the printing ink. Heat is conducted away from the platen through the thermally conductive platen 22 through the moving paper 12. At the same time, the moving paper 12 facilitates convection cooling of the thermally conductive platen 22. When printing demands increases, more heat is generated within the printer, and more drying capacity is available. Also, more paper 12 will be fed over the thermally conductive platen 22 thereby causing the heat to be removed at a faster rate commensurate with the additional heat being generated. Having illustrated and described the principles of my invention in a preferred embodiment thereof, it should be readily apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. I claim all modifications coming within the scope of the accompanying claims.

Claims: A method for drying ink deposited onto a printing medium (12), which comprises the steps of: providing a printer for depositing ink onto said printing medium (12), said printer including a primary heat generating module (30) and a thermally conductive platen (22); mounting a thermally conductive clip (24) on the thermally conductive platen (22); mounting the primary heat generating module (30) on a printed circuit board (26); mounting the primary heat generating module (30) on the clip (24) such that heat from the primary heat generating module (30) is conducted through the clip (24) to the thermally conductive platen (22); moving said printing medium (12) into contact with said heated thermally conductive platen (22) so as to thereby heat said printing medium (12); depositing said ink onto said heated printing medium (12); and drying the ink on said heated printing medium (12), the printing medium (12) and the thermally conductive platen (22) acting so as to conduct away heat not dissipated in said ink drying step from the thermally conductive platen (22) through movement of the printing medium (12), the moving printing medium (12) generating a convection current over the thermally conductive platen (22). The method of claim 1, wherein the thermally conductive clip (24) is a metal clip. The method of claim 1 or claim 2, which further includes the step of moving said printing medium (12) over the thermally conductive platen (22) and thereby removing heat build up within the printer, the heat removal rate being commensurate with the rate of heat generation in the printer. The method of any one of claims 1 to 3, wherein the ink comprises a liquid-based ink. The method of any one of claims 1 to 4, wherein the primary heat generating module (30) comprises a power supply or a motor. A printer for depositing printing ink onto said printing medium (12), which comprises means for depositing printing ink onto said printing medium (12); a thermally conductive platen (22) onto which the printing medium (12) is moved into contact during deposition of the ink onto the printing medium (12); a thermally conductive clip (24) mounted on the thermally conductive platen (22); and a primary heat generating module (30) mounted on a printed circuit board (26), the primary heat generating module (30) being mounted on the clip (24) such that heat from the primary heat generating module (30) is conducted through the clip (24) to the thermally conductive platen (22) so as to thereby dry said ink on the primary medium (12), and the printing medium (12) and the thermally conductive platen (22) acting so as to conduct away heat not dissipated during drying of the said ink from the thermally conductive platen (22) through movement of the printing medium (12), the moving printing medium (12) generating a cooling air convection current over the thermally conductive platen (22), which current dissipates heat built up within the printer. The printer of claim 6, wherein the thermally conductive clip (24) is a metal clip. The printer of claim 6 or claim 7, which further includes means for removing heat build up from within the printer when said printing medium (12) is moved over the thermally conductive platen (22) so that the rate of removal of heat build up is commensurate with the rate of heat generated in the printer. The printer of any one of claims 6 to 8, wherein the ink comprises a liquid-based ink. The printer of any one of claims 6 to 9, wherein the primary heat generating module (30) comprises a power supply or motor.

Inventors: CHAN JAMES LOKE KIE, LIM CHUIN KIAT, CHAN, JAMES LOKE KIE, LIM, CHUIN KIAT
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1993
Main classification: B41J2
IPC codes: B41J29, B41J2, B41J11