Thermal inkjet printer having enhanced heat removal capability and method of assembling the printer

#This invention generally relates to printer apparatus and methods and more particularly relates to a thermal ink jet printer having enhanced heat removal capability and method of assembling the printer, the printer being adapted for high speed printing and increased thermal resistor lifetime.

#An ink jet printer produces images on a recording medium by ejecting ink droplets onto the recording medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the ability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.

#In the case of thermal inkjet printers, a print head structure comprises a single or plurality of ink cartridges each having a nozzle plate that includes a plurality of nozzles. Each nozzle is in communication with a corresponding ink ejection chamber formed in the print head cartridge. Each ink ejection chamber in the cartridge receives ink from an ink supply reservoir containing, for example, yellow, magenta, cyan or black ink. In this regard, the ink supply reservoir may be internal to the cartridge and thus define an “on board” or internal ink reservoir. Alternatively, each cartridge may be fed by conduit from an “off-axis” or remote ink supply reservoir. In either event, each ink ejection chamber is formed opposite its respective nozzle so ink can collect between the ink ejection chamber and the nozzle. Also, a resistive heater is disposed in each ink ejection chamber and is connected to a controller, which selectively supplies sequential electrical pulses to the heaters for actuating the heaters. When the controller supplies the electrical pulses to the heater, the heater heats a portion of the ink adjacent the heater, so that the portion of the ink adjacent the heater vaporizes and forms a vapor bubble. Formation of the vapor bubble pressurizes the ink in the ink ejection chamber, so that an ink drop ejects out the nozzle to produce a mark on a recording medium positioned opposite the nozzle.

#While the specification concludes with claims particularly pointing-out and distinctly claiming the subject matter of the present invention, it is believed the invention will be better understood from the following description when taken in conjunction with the accompanying drawings wherein:

#FIG. 1 is a view in perspective, with parts removed for clarity, of a thermal inkjet printer according to the present invention, the printer comprising a print head including a plurality of ink cartridges;

#FIG. 2 is a view in elevation of a first embodiment of a representative one of the cartridges;

#The present invention will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.

#Therefore, referring to FIG. 1, there is shown a thermal inkjet printer, generally referred to as 10, for printing an image 20 on a recording medium 30. Recording medium 30 may be a reflective recording medium (e.g., paper) or a transmissive recording medium (e.g., transparency) or other type of recording medium suitable for receiving image 20. Printer 10 comprises a housing 40 having a first opening 45 and a second opening 47 therein for reasons disclosed presently. Disposed in housing 40 is an upright frame 50 defining an aperture 55 therein for reasons disclosed presently. Connected to frame 50 is a first motor 60, which may be a stepper motor, engaging an elongate spindle 70 for rotating spindle 70. Fixedly mounted on spindle 70 are a plurality of rollers 80 that rotate as spindle 70 is rotated by first motor 60. Also connected to frame 50 is an elongate slide bar 90 oriented parallel to spindle 70. Slidably engaging slide bar 90 is an ink cartridge holder 100 adapted to hold a plurality of generally rectangularly-shaped ink cartridges 110a, 110b, 110c and 110d. Ink cartridges 110a, 110b, 110c and 110d contain colorants such as yellow, magenta, cyan and black ink, respectively.

#Referring again to FIG. 1, a belt drive assembly, generally referred to as 120, is also connected to frame 50. Belt drive assembly 120 comprises a plurality of oppositely disposed rollers 130a and 130b rotatably connected to frame 50. One of the rollers, such as roller 130b, engages a reversible second motor 140, which may be a stepper motor, for rotating roller 130b. In this case, roller 130a is configured to freely rotate while roller 130b is rotated by second motor 140. Wrapped around rollers 130a and 130b and spanning the distance therebetween is a continuous belt 150 affixed to ink cartridge holder 100. Thus, it may be appreciated from the description hereinabove, that operation of second motor 140 will cause roller 130b to rotate because roller 130b engages second motor 140. Belt 150 will rotate as roller 130b rotates because belt 150 engages roller 130b. Of course, roller 130a will also rotate as belt 150 rotates because roller 130a engages belt 150 and is freely rotatable. In this manner, cartridge holder 100 will slide to-and-fro or reciprocate along slide bar 90 as reversible second motor 140 rotates belt 150 first in a clockwise direction and then in a counter-clockwise direction. This to-and-fro reciprocating motion allows cartridge holder 100 and cartridges 110a/b/c/d held by cartridge holder 100 to traverse the width of recording medium 30 to print a swath of information on recording medium 30. After printing the swath of information, spindle 70 and associated rollers 80 rotate in the manner disclosed hereinabove to advance recording medium 30 the width of the swath and print another swath of information. This process is repeated until the desired image 20 is printed on recording medium 30. Also connected to frame 50 is a controller 160. Controller 160 is electrically coupled, such as by means of an electricity flow path or wire 170a, to ink cartridges 110a/b/c/d for selectively controlling operation of ink cartridges 110a/b/c/d, so that ink cartridges 110a/b/c/d eject an ink drop 180 on demand (see FIG. 2). Moreover, as shown in FIG. 1, controller 160 is electrically coupled, such as by means of an electricity flow path or wire 170b, to second motor 140 for controlling operation of second motor 140. In addition, controller 160 is electrically coupled to first motor 60, such as by means of another electricity flow path or wire (now shown), for controlling operation of first motor 60. Further, controller 160 is coupled to a picker mechanism (not shown) belonging to printer 10 for controlling operation of the picker mechanism. The picker mechanism “picks” individual sheets of recording medium 30 from a recording medium supply bin or tray 190 insertable into housing 40 through second opening 47. In this regard, the picker mechanism will “pick” and then feed an individual sheet of recording medium 30 from supply tray 190, through aperture 55 and into engagement with rollers 80, so that the sheet of recording medium 30 is interposed between ink cartridges 110a/b/c/d and rollers 80. Thus, it may be appreciated from the description hereinabove, that controller 160 controls synchronous operation of first motor 60, second motor 140, the picker mechanism and ink cartridges 110a/b/c/d for producing desired image 20 on recording medium 30. Input to controller 160 may be from an image processor, such as a personal computer or scanner (not shown).