Hot-melt type ink jet printer having heating and cooling arrangement

Information

  • Patent Grant
  • 6196672
  • Patent Number
    6,196,672
  • Date Filed
    Wednesday, June 17, 1998
    26 years ago
  • Date Issued
    Tuesday, March 6, 2001
    23 years ago
Abstract
A hot-melt type ink jet printer includes a nozzle head for ejecting a hot-melt type ink onto a sheet. The printer has a sheet feed passage defined by, in order from an upstream side in a sheet feeding direction, a sheet supply roller, a preheat platen, a sheet feed roller, a main platen, a cooling platen, discharge roller and a sheet discharge opening. The preheat platen and main platen have preheater and main heater, respectively, and these platen and the cooling platen are supported on a frame. A first suction port is formed between the main platen and the cooling platen and a second suction port is formed between the cooling platen and the frame. A power board and a cooling fan is provided within the frame for cooling the power board. By rotation of the cooling fan, air is introduced from the sheet discharge opening into the frame through the first and second suction ports to also cool the cooling platen and the heating platen.
Description




BACKGROUND OF THE INVENTION




The present invention relates to an ink-jet printer using hot-melt type ink and capable of heating a recording medium such as a paper and cooling the recording medium after the hot-melt type ink has been printed on the recording medium.




A conventional hot-melt type ink-jet printer includes a recording head mounted on a carriage. The recording head includes a nozzle head having a plurality of nozzles, an ink melting section including a heater, and a hopper for storing solid ink pellets. Further, a platen is provided in confrontation with the nozzle head for supporting the recording medium. The carriage is moved in a main scanning direction orthogonal to a recording medium feeding direction, while hot-melt ink droplets are ejected from the nozzles in the nozzle head to form images such as characters and graphs on the surface of the recording medium. The hot melt ink, once printed on a print medium, is extremely durable and has a weather proof characteristic. Hot-melt ink liquefies when heated and hardens at room temperature. Therefore, to print using hot melt ink, the hot melt ink in the print head is heated and melted before it is ejected from the print head.




If the hot-melt ink is ejected from the nozzle heads onto the surface of the recording medium having a relatively low temperature, the ink droplet is immediately solidified at the surface. Therefore, ink fixing property on the recording medium may be lowered. Thus, the solidified ink may be easily peeled off from the surface of the recording medium to degrade the imaging quality. In this connection, the recording medium must be sufficiently heated prior to the ink ejection. To this effect, conveying speed of the recording medium must be low prior to the printing operation to obtain sufficient heat transmission to the recording medium. As a result, high speed printing cannot be performed.




If the hot-melt ink is ejected onto pre-heated recording medium having a prescribed elevated temperature, the fixing properties of the ink on the recording medium can be improved. However, downstream of the recording head, the recording medium continues to be fed between a discharge roller and a pinch roller. If the hot-melt ink fixed on the recording medium has not solidified completely before passing through these rollers, some of the ink is transferred to the pinch roller and the like, thereby reducing the quality of the printed image.




In order to avoid these problems, in a subsequent conventional printer, a heater is provided at a back side of the platen opposite a side along which the recording medium passes for increasing the temperature of the recording medium. Further, a sheet conveying distance between the platen and a discharge section including the discharge roller and the pinch roller is designed to be longer to allow the recording medium just printed to cool while being conveyed over this longer distance. This allows the hot-melt ink to solidify before reaching the discharge section.




However, in order to lengthen the conveying distance, it is necessary to increase the overall dimensions of the printer. Moreover, if the conveying speed of the recording medium is increased after printing operation, the time required to convey the recording medium from the printing portion to the discharge section is essentially decreased. As a result, it is impossible to achieve the cooling effect when performing high-speed printing on a printer of this construction and, therefore, impossible to achieve an image of desirable quality.




Further, in a conventional hot-melt type ink jet printer, a power board is provided in a main case of the printer. Since a temperature of the power board tends to be elevated, a cooling fan is provided in the main case to cool the power board by blowing air on the same. The cooling fan is disposed in a wall of the main case, from which location external air can be easily taken in or expelled.




U.S. Pat. No. 5,005,025 discloses an ink jet printer having a heater whose upstream part serves as a platen and whose downstream part extending to a discharge roller. Because the heater provides an elongated conveying path, sufficient heat can be transmitted to the recording medium for improving fixation.




SUMMARY OF THE INVENTION




In view of the foregoing, it is an object of the present invention to provide a hot-melt type ink jet printer compact in size and capable of performing high speed printing yet maintaining high imaging quality.




Further, attention is drawn to the utilization of the cooling fan which conventionally is used for cooling the power board. In the present invention, the recording medium must be sufficiently heated immediately before the ink ejection for improving the image-fixing. On the other hand, the fixed inked image must be immediately cooled to avoid ink transfer to the sheet discharge section. Thus, another object of the present invention is to provide the hot-melt type ink jet printer including the cooling fan which generates a stream of air for cooling not only the power board but also the recording medium so as to promote cooling of the recording medium, thereby allowing the formation of high quality images on the recording medium even during high-speed printing.




Still another object of the present invention is to provide such printer capable of providing a suitable heating temperature, a suitable cooling temperature, a suitable printing speed of the recording medium and a suitable discharge timing of the recording medium.




Still another object of the present invention is to provide such printer capable of performing efficient cooling to a power board provided in a printer frame.




These and other objects of the present invention will be attained by providing a hot-melt type ink jet printer for forming an inked image on an image receiving medium including a frame, a nozzle head, a main platen, a cooling platen, and a discharge roller. The nozzle head is movable relative to the frame and ejects a hot-melt ink onto the image receiving medium. The main platen has one surface in confrontation with the nozzle head. The image receiving medium is fed in a feeding direction along the one surface. The cooling platen is positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium. The discharge roller is disposed downstream of the cooling platen for discharging the image receiving medium. The frame havs has a sheet discharge opening adjacent the discharge roller. An order of the main platen, the cooling platen and the discharge roller defines a sheet feed passage.




In another aspect of the invention, there is provided a hot-melt type ink jet printer for forming an inked image on an image receiving medium including a frame having a front side and a rear side, a nozzle head, a main platen, a main heater, a second platen, a fan, and a power board. The nozzle head is movable relative to the frame and ejects a hot-melt ink onto the image receiving medium. The main platen has one surface in confrontation with the nozzle head. The image receiving medium is fed in a feeding direction along the one surface. The main heater is provided at the opposite surface of the main platen for heating the main platen. The second platen is disposed immediately downstream of the main platen. A combination of the main platen and the second platen defines a sheet feed passage extending toward the front side of the frame. A first suction port is formed between the main platen and the second platen for introducing a cooling air into an interior of the frame through the first suction port. A second suction port is formed at the front side of the frame. The first suction port is open to the sheet feed passage and the second suction port is open to the front side. The fan is positioned at an intermediate portion between the front side and the rear side of the frame. The power board is positioned between the fan and the rear side of the frame. The power board is cooled by the cooling air introduced into the frame by the fan through the first suction port and the second suction port.











BRIEF DESCRIPTION OF THE DRAWINGS




In the drawings:





FIG. 1

is a perspective view showing a hot-melt type ink jet printer according to a preferred embodiment of the present invention;





FIG. 2

is a side cross-sectional view of the hot-melt type ink-jet printer in

FIG. 1

;





FIG. 3

is a plan view showing the positional relationship of a carriage, an ink case, and a maintenance operation portion according to the embodiment;





FIG. 4

is an enlarged cross-sectional view showing the relevant parts along a sheet feed passage according to the embodiment;





FIG. 5

is a side view of a main platen, a cooling platen, and a support frame according to the embodiment;




FIG.


6


(


a


) is a cross-sectional view taken along the line VIA—VIA of

FIG. 3

;




FIG.


6


(


b


) is a cross-sectional view taken along the line VIB—VIB of

FIG. 3

;





FIG. 7

is a block diagram showing a control system according to the embodiment;





FIG. 8

is a flowchart representing a process for controlling a sheet supply timing;





FIG. 9

is a flowchart representing a process for controlling sheet supply timing and sheet discharge timing according to a modified control routine;





FIG. 10

is a flowchart representing a process for controlling sheet supply timing and a temperature of a heat platen according to another modified control routine; and





FIG. 11

is a flowchart representing a process for controlling sheet supply timing and a printing speed according to a still another modified control routine.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




A hot-melt type ink-jet printer according to a preferred embodiment of the present invention will be described while referring to

FIGS. 1 through 7

.




As shown in

FIG. 1

, a hot-melt type ink jet printer


1


includes a main case


1




a


, a sheet supply unit


3


(another sheet supply unit


2


is shown in FIG.


2


), an operation panel


4


, a discharge tray


6


, an upper cover


7


and a cover


9


. The main case


1




a


has a top wall where a center opening


1




b


is formed. The sheet supply units


2


and


3


are detachably mounted in a top back portion of the main case


1




a


for accommodating stacks of recording mediums P, such as ordinary cut-sheet paper, transparent films for overhead projectors, and the like. The operation panel


4


is provided with various operating switches disposed on a right side top surface of the main case


1




a


. A sheet discharge opening


5


is formed on the front surface of the main case


1




a


, and the discharge tray


6


is provided to the opening


5


to receive the recording medium P after a printing operation.




The upper cover


7


is disposed on the top surface of the printer


1


and is capable of opening and closing to reveal or cover the center opening


1




b


. An ink case


8


serving as an ink pellet supply portion is detachably mounted in a left side of the center opening


1




b


. The ink case


8


contains a plurality of accommodation grooves


8




a


arranged in a row and capable of accommodating ink pellets (not shown) of the various colors of yellow, magenta, cyan, and black. The cover


9


is disposed on the top surface of the main case


1




a


and is capable of opening and closing in order to reveal and cover the top surface of the ink case


8


. A transparent cover


10


is fixed on the right side of the ink case


8


and covers the right side of the center opening lb. The transparent cover


10


is formed with a plurality of vent slots


10




a.






Next, an internal arrangement of the printer will be described with reference to FIG.


2


. First, the sheet supply units


2


and


3


are arrayed in a frontward/rearward direction of the printer


1


. Manual insertion trays


2




a


and


3




a


are provided in the top surface of the sheet supply units


2


and


3


, respectively. A semi-circular or sector shaped sheet supply rollers


22




a


and


22




b


are disposed on the lower ends of the sheet supply units


2


and


3


, respectively. A recording medium P either stacked in the sheet supply units


2


or


3


, or hand-fed into the manual insertion tray


2




a


or


3




a


, is conveyed along a sheet feed passage


29


. The sheet feed passage


29


is defined in order from upstream to downstream in a sheet feed direction, a register roller pair


23




a


and a register roller pair


23




b


, an optical sensor


45


, a sheet feed roller


25


and pinch roller


25




a


, a main platen


26


, a cooling platen


27


, a discharge roller


28


and pinch roller


28




a


, a discharge sensor


55


, the sheet discharge opening


5


and the discharge tray


6


. A print head


11


is mounted on a carriage


12


. The print head


11


includes a nozzle head


13


in confrontation with the main platen


26


. A carriage motor


60


(

FIG. 7

) is provided for moving the nozzle head


13


back and forth in the main scanning direction.




A frame


34


is provided approximately in the front-to-back central section of the main case


1




a


, forming a hollowed space. Discharge ports


40


and


41


are formed in the back surface of the frame


34


and a back surface of the main case


1




a


, respectively. A cooling fan


35


is provided in an approximately center portion of the frame


34


and on the back side of both the main platen


26


and cooling platen


27


for introducing cooling air in the direction from the sheet discharge opening


5


into the interior of the frame


34


. Further, a power board


42


is disposed within the frame


34


and between the cooling fan


35


and the discharge ports


40


and


41


. Therefore, the power board


42


can be cooled by the cooling air introduced by the cooling fan


35


. The discharge ports


40


and


41


are positioned so that an approximately linear air stream can be provided in the frame


34


between suction ports (described later) and the discharge ports


40


,


41


. Thus, flowing air can be concentrated into the linear stream within the frame


34


.




As shown in

FIG. 4

, the print head


11


includes the nozzle head


13


, a front panel


14


, an ink tank


15


, a melt hopper


16


, a lid panel


17


, and a relay portion


18


. The front panel


14


is formed with ink transport channels, and has a lower side supporting the nozzle head


13


. The ink tank


15


is adapted for supplying ink to the nozzle head


13


. An ink sensor (not shown) is provided in the ink tank so as to detect an ink level in the ink tank. The melt hopper


16


is adapted for melting ink pellets and refilling the ink tank


15


. The lid panel


17


is adapted for covering the outer surface side of the front panel


14


. The relay portion


18


is provided with a control circuit for controlling piezoelectric elements for executing ink ejection from the nozzle head


13


, various heaters (described later), and the like.




A panel heater


14




a


is provided on an upper side of the front panel


14


for heating the ink transport channels. A heater


15




a


is provided on the outside of the ink tank


15


for maintaining the hot-melt ink at an appropriate temperature. A heater


16




a


is provided on the outside of the melt hopper


16


for melting the ink pellets.




A guide shaft


19


and a guide rail


20


extend in a lateral direction of the printer


1


. The carriage


12


is driven to move in a back and forth direction (the lateral direction) according to a transport mechanism (not shown). The carriage


12


moves within the main case


1




a


in the sub scanning direction (orthogonal to the sheet feed direction), guided along the guide shaft


19


and the guide rail


20


.




An ink pellet supply mechanism (not shown) is disposed below the front end of the ink case


8


. During printing operations, ink is consumed, thereby reducing the amount of the various colors of hot-melt ink contained in the ink tank


15


. When the ink sensors (not shown) detect that an ink color is running out, the carriage


12


is moved so as to position the section of the melt hopper


16


corresponding to the section of the ink tank


15


running out of ink below the portion of the ink case


8


storing the corresponding color of ink pellets. At this time, a driving section of the ink pellet supply mechanism is operated to release solid ink pellets of the prescribed color from the ink case


8


into the melt hopper


16


. The ink pellets can maintain its solid state at a room temperature.




In addition, as shown in

FIG. 3

, a maintenance operation portion


21


is disposed on the right end in the main case


1




a


for purging the nozzles of the nozzle head


13


in order to prevent blockage of the nozzles during normal printing operations. This purge operation is accomplished by positioning the carriage


12


in a prescribed position and ejecting ink from the nozzles onto a testing roll paper provided in the maintenance operation portion


21


. Further, as shown in

FIG. 3

, the sheet feed roller


25


and the discharge roller


28


are not continuous but are provided in regular intervals on support shafts


25




b


and


28




b


, respectively.




As shown in FIGS.


3


through


6


(


b


), a support frame


30


is mounted on top of the frame


34


. The support frame


30


is formed of a heat resistant synthetic resin material, such as polyetherimide, polyamideimide, polyimide, or the like. As shown in FIGS.


6


(


a


) and


6


(


b


), the support frame


30


has a bottom plate


30




c


, projecting portions


30




a


and


30




b


provided at left and right sides of the bottom plate


30




c


and projecting upwardly therefrom, a protrusion


30




d


projecting upwardly from the bottom plate


30




c


and at a widthwise center thereof, and a front wall plate


30




e


. The main platen


26


and the preheat platen


24


are provided integrally with each other. As shown in

FIG. 3

, a single plate member is sectioned into two areas by the sheet feed roller


25


to provide the main platen


26


and the preheat platen


24


positioned upstream of the main platen


26


. More specifically, a plurality of elongated through holes are formed in the single plate member, and each sheet feed rollers


25


is disposed in each elongated through hole as shown in FIG.


3


.




Left and right sides of the main platen


26


and the preheat platen


24


are supported onto the support frame


30


and is fixedly secured to the projecting portion


30




a


by screws


31


as shown in FIGS.


3


and


6


(


a


). The preheat platen


24


and the main platen


26


are provided with a pre-heater


24




a


and main heater


26




a


on the back sides thereof, respectively for heating the recording medium P from the back sides. A surface temperature of the preheat platen


24


is preferably set higher than that of the main platen


26


. Further, a pre-thermistor


69


and a main thermistor


70


(

FIG. 7

) are provided adjacent the preheat platen


24


and the main platen


26


, respectively, for detecting a temperature of the preheat platen


24


and the main platen


26


, respectively.




The cooling platen


27


is provided downstream of the main platen


26


in the sheet feeding direction for positively cooling the printed recording medium P when the latter is moved therealong in intimate contact therewith. Accordingly, ink transfer from the printed recording medium P to the discharge roller


28


and the pinch roller


28




b


can be avoided even by the high speed printing. The cooing platen


27


can reduce entire path length of the sheet feed passage from the main platen


26


to the discharge roller


28


because of the sufficient cooling effect.




Left and right sides of the cooling platen


27


are supported on the support frame


30


. More specifically, the cooling platen


27


has recessed portions


27




a


(FIG.


6


(


a


)) at left and right sides thereof and in confrontation with the projecting portion


30




b


of the support frame


30


, and a screw


32


extends through each recessed portion


27




a


and threadingly engaged with the projecting portion


30




b


, so that the cooling platen


27


is unreleasably connected to the support frame


30


but can be movable toward and away from the top surface of the support frame


30


only a minute distance H


1


(about 0.1-0.2 mm in the present embodiment). As shown in FIG.


6


(


b


), a coil spring


33


is disposed between the widthwise central underside portion of the cooling platen


27


and the protrusion


30




d


of the support frame


30


so that the cooling platen


27


is urged by the coil spring


33


to protrude toward the nozzle head


13


. The cooling platen


27


has a plurality of cooling fins


27




b


described later.




The preheat platen


24


, main platen


26


, and cooling platen


27


should be formed of a metallic material having high thermal conductivity, such as aluminum. At least the main platen


26


and the cooling platen


27


should have an outer surface (the surface contacting the underside of the recording medium P) formed in the shape of a convex curve with a radius R that protrudes toward the nozzle head


13


. In the present embodiment, the preheat platen


24


and main platen


26


are formed as one piece, and therefore, the outer surface of the preheat platen


24


can also be formed in a convex shape with the radius R.




According to the construction described above, the recording medium P on the upstream side of the sheet feed passage


29


is pinched between the sheet feed roller


25


and pinch roller


25




a


, while the recording medium P on the downstream side of the sheet feed passage


29


is pinched between the discharge roller


28


and pinch roller


28




a


. Thus, tension is applied to the recording medium P as the same is conveyed along the sheet feed passage


29


. Therefore, the entire underside surface of the recording medium P is supported and contacted by the convex surfaces formed by the preheat platen


24


, the main platen


26


, and the cooling platen


27


. Therefore, thermal transfer can be executed efficiently from the surfaces of the preheat platen


24


and main platen


26


to the recording medium P. Similarly, thermal absorption (cooling) can be executed efficiently from the surface of the recording medium P to the cooling platen


27


.




Further, when the recording medium P is conveyed along the sheet feed passage


29


by the sheet feed roller


25


and pinch roller


25




a


and the discharge roller


28


and pinch roller


28




a


, the entire surface of the cooling platen


27


along the conveying direction is pressed against the underside surface of the recording medium P by the biasing force of the coil spring


33


. As a result, heat can be effectively transferred from the recording medium P to the cooling platen


27


. Since the entire contour of the preheat platen


24


, the main platen


26


and the cooling platen


27


provides a smooth arcuate configuration protruding toward the nozzle head


13


, and since the recording medium P is conveyed along the arcuate surface in intimate contact therewith without any floating, and since the efficient heating and cooling can be performed, high speed feeding and high speed printing can be achieved. Because floating of the recording medium P can be avoided, the recording medium P is not trapped by the nozzle head even if a distance between the nozzle head


13


and the main platen


26


is set small. Accordingly, sheet jamming can be avoided.




The rotating speed of the discharge roller


28


is set faster than that of the sheet feed roller


25


. Further, the pinching force between the discharge roller


28


and pinch roller


28




a


is set weaker than that between the sheet feed roller


25


and pinch roller


25




a


. Accordingly, the discharge roller


28


and the pinch roller


28




a


slip on the recording medium P enough to allow for the difference in speed from the rollers


25


and


25




a


. Although the pinching pressure between the rollers


28


and


28




a


is set lower, sufficient pressure is applied to prevent the recording medium P from floating up from the sheet feed passage


29


by the urging force of the cooling platen


27


, which is resiliently urged by the coil springs


33


.




As shown in

FIG. 5

, a main baffle


43


and an auxiliary baffle


44


are fixed at positions in a main case


1




a


for assuring intimate contact of the recording medium P with the platens


24


,


26


. The main baffle


43


has an intermediate portion formed with slots in which the pinch rollers


25




a


are disposed. The main baffle


43


has a free end in pressure contact with the upper surface of the main platen


26


. The auxiliary baffle


44


has a free end in pressure contact with the upper surface of the preheat platen


24


. These baffles


43


and


44


ensure that the recording medium P is more reliably prevented from floating above the sheet feed passage


29


. The baffles


43


and


44


can be constructed from a heat resistant and resilient synthetic resin material such as polyimide film. However, in the present embodiment, a thin metal plate having a sufficient rigidity is used. For example, a phosphor bronze plate having a thickness of 0.1 mm is used for the main baffle


43


, while a stainless steel plate having a thickness of 0.1 mm is used for the auxiliary baffle


44


. Although the main baffle


43


does not necessarily need to be composed of phosphor bronze, better experiment results were obtained with this material than when using stainless steel. This may be due to the difference in thermal conductivity. Further, either one of the main baffle


43


and the auxiliary baffle


44


can be dispensed with.




In the depicted embodiment, a cooling air stream is provided by the cooling fan


35


. To this effect, suction ports (described later) are formed at a position downstream of the main platen


26


. Thus, upon rotation of the cooling fan


35


, external air is introduced into the main case


1




a


through the sheet discharge opening


5


and is then introduced into the frame


34


through the suction ports, and the introduced air is discharged to the atmosphere through the discharge ports


40


and


41


. The air stream runs toward the cooling platen


27


to cool the same.




More specifically, as shown in

FIGS. 2

,


4


,


6


(


a


), and


6


(


b


), the cooling fan


35


is disposed within the hollow frame


34


, which is positioned below the sheet feed passage


29


and approximately in the front-to-back center of the main case


1




a


. The support frame


30


is mounted in the top forward portion of the frame


34


. By positioning the main platen


26


fixed to the support frame


30


and the cooling platen


27


so as to be separated by a prescribed distance, a first suction port


36


is formed along the width of the nozzle head


13


in the sub scanning direction and between the downstream end of the main platen


26


and the upstream end of the cooling platen


27


. An elongated adiabatic partition plate


38


composed of a heat-resistant synthetic resin is disposed in the first suction port


36


, thermally separating the downstream end of the main platen


26


and the upstream side of the cooling platen


27


.




A plurality of second suction ports


37


is formed between the bottom surface of the cooling platen


27


on the downstream end and at the front wall plate


30




e


of the support frame


30


. The second suction ports


37


are spaced at appropriate intervals along the sub scanning direction of the nozzle head


13


at appropriate lengths between the sections of the discharge roller


28


. In other words, the second suction ports


37


correspond to bare portions of the support shaft


28




b


not containing sections of the discharge roller


28


. Incidentally, the discharge roller


28


need not be limited to four locations along the support shaft


28




b


(FIG.


3


), but can be distributed in six or more locations along the support shaft


28




b


. Also, the second suction ports


37


need not be limited to the intervals between the sections of the discharge roller


28


, but can be formed as one long second suction port


37


that spans the entire width of the cooling platen


27


. The plurality of cooling fins


27




b


(see FIG.


6


(


b


)) are provided to the underside surface of the cooling platen


27


in positions opposing the second suction ports


37


in order to promote cooling of the cooling platen


27


by the cooling air passing through the second suction port


37


because a cooling area is increased by the area of the cooling fins


27




b.






An air passage hole


39


is formed in the bottom plate


30




c


, providing fluid communication between the first suction port


36


and the second suction ports


37


and guiding cooling air to the cooling fan


35


, as shown in

FIGS. 4

,


6


(


a


), and


6


(


b


). The adiabatic partition plate


38


extends into the air passage hole


39


so as to ensure heat separation from the heat of the main platen


26


. The support frame


30


serves different functions, i.e., serves for allowing air to pass therethrough as well as for supporting the platens


24


,


26


and


27


. Therefore, parts or components of the printer can be reduced.




The optical sensor


45


(

FIG. 2

) is of a light-transmission type, and is provided along the sheet feed passage


29


between the register roller pair


23




b


and the preheat platen


24


in order to determine the type of recording medium P. In other words, the optical sensor


45


is provided to determine if the recording medium P is normal paper or transparent paper, such as transparent film used in overhead projectors. The optical sensor


45


outputs detection signals to control the temperature conditions of a heater described later. The discharge sensor


55


(

FIG. 2

, FIG.


6


(


b


)) is provided at a position adjacent the pinch roller


28




a


for detecting discharge of the recording medium P. Further, a temperature sensor


56


is provided to the undersurface of the cooling platen


27


as shown in FIG.


6


(


b


). The temperature sensor


56


serves to detect the temperature of the cooling platen


27


.




Next, the control system of a hot-melt type ink jet printer having the construction described above will be described with reference to the block diagram in FIG.


7


.




The control system includes a CPU


50


, a ROM


51


, a RAM


52


and various driver circuits. The CPU


50


executes various computation and control operations necessary for printing color images based on print data transmitted from a host computer (not shown). The operations are executed according to various control programs stored in the ROM


51


. The ROM


51


stores various control programs and settings for control temperatures of the preheat platen


24


and/or main platen


26


corresponding to the type of recording medium P and the printing resolution. The ROM


51


also stores a head control program for controlling drive of a carriage driver circuit


63


and a print head driver circuit


62


. The RAM


52


is adapted for temporarily storing print data sent from the host computer and temporarily serves as a work area for executing various control routine.




To the CPU


50


are connected a print head driver circuit


62


, a carriage driver circuit


63


, a heater control circuit


64


, a fan driver circuit


65


, a feed system driver circuit


66


, and a sheet supply system driver circuit


68


. The print head driver circuit


62


is adapted for driving the nozzle head


13


based on print data at a predetermined timing to eject ink from the nozzle head


13


in order to print predetermined images such as characters. The carriage driver circuit


63


is adapted for driving the carriage motor


60


to move the carriage


12


reciprocally in the main scanning direction. The heater control circuit


64


is adapted for controlling electrical supply to the pre-heater


24




a


and the main heater


26




a


. The fan driver circuit


65


is adapted for driving the cooling fan


35


. The feed system driver circuit


66


is adapted for driving a sheet feed motor


61


. For example, when the sheet feed motor


61


is rotated in a normal direction, the sheet feed roller


25


and discharge roller


28


are rotated in the sheet feeding direction, and if the sheet feed motor


61


is reversely rotated, the ink supply mechanism or the maintenance operating portion


21


is selectively operated. Thus, is controlled the feed mode of the recording medium P in an auxiliary scanning direction, which is substantially perpendicular to the reciprocal scan direction of the carriage


12


, so that the recording medium P is moved past the print head


11


and onto the discharge tray


6


. The sheet supply system driver circuit


68


is adapted for driving a sheet supply solenoid


67


which selectively operates one of the sheet supply rollers


22




a


and


22




b


in order to feed the recording medium P along the sheet feed passage


29


. Further, the pre thermistor


69


for detecting the temperature of the preheat platen


24


and the main thermistor


70


for detecting the temperature of the main platen


26


are connected to the CPU


50


. Furthermore, the optical sensor


45


, the discharge sensor


55


and the temperature sensor


56


are also connected to the CPU


50


. The pre thermistor


69


, main thermistor


70


, and optical sensor


45


are configured to output prescribed control signals for either the heater control circuit


64


or the fan driver circuit


65


based on the various detection signals described above.




Next, heating and cooling operations conducted according to the above-described configuration will be described. When a power switch (not shown) on the printer


1


is rendered ON, the printer


1


enters a standby state for printing operation. The printer


1


begins heating operations by flowing an electric current to the pre-heater


24




a


and main heater


26




a


and also begins rotating the cooling fan


35


. Air drawn in through the sheet discharge opening


5


is introduced into the sheet feed passage


29


and the downstream side of the cooling platen


27


. The air then enters the frame


34


via both the first suction port


36


and the second suction ports


37


because during this standby state the first suction port


36


is not blocked by the recording medium P. The air passes through the air passage hole


39


, and is drawn through the cooling fan


35


, and finally is exhausted out of the back side of the main case


1




a


. That is, the cooling air flows along the surface of the power board


42


absorbing heat from the same and is exhausted out of the main case


1




a


via the discharge ports


40


and


41


. During the standby state, the number of revolutions of the cooling fan


35


is reduced to less than that during printing operations, and electrical supply to the pre-heater


24




a


and main heater


26




a


is also reduced to lower power consumption. Further, during initial start-up period of the printer


1


, suction amount of the cooling air can be reduced so as to rapidly elevate the temperature of the main platen


26


.




When printing operations are begun, electrical power supply to the pre-heater


24




a


and main heater


26




a


is returned to a prescribed amount in order to maintain the preheat platen


24


and main platen


26


at prescribed temperatures. When the printer


1


receives a paper supply command, after selection of the type of recording medium P, the specified sheet supply roller


22




a


or


22




b


is rotated to feed the leading edge of the selected recording medium P as far as either the register roller pair


23




a


or register roller pair


23




b


. After the leading edge of the recording medium P is registered, that is, after the diagonal feeding of the recording medium P is corrected, the recording medium P is conveyed toward the sheet feed roller


25


.




The recording medium P is pressed against the surface of the preheat platen


24


by the resilient auxiliary baffle


44


and is preheated. Next, the recording medium P is pressed against the surface of the main platen


26


by the main baffle


43


and receives a main heating. When the leading edge of the recording medium P passes over the first suction port


36


, the underside surface of the recording medium P does not float above the convex curved surface of the main platen


26


because suction force is imparted to the recording medium P. Hence, the recording medium P can reliably be heated by the main platen


26


.




In this way, the recording medium P is intimately contacted with and supported by the preheat platen


24


and main platen


26


and is heated to a specified temperature while being fed. Since the recording medium P is heated, hot-melt ink ejected from the nozzle head


13


, which opposes the main platen


26


, fixes readily to the recording medium P. Next, when the recording medium P becomes nipped between the discharge roller


28


and the pinch roller


28




a


, the first suction port


36


is completely blocked by the recording medium P. Therefore, almost no air flows through this first suction port


36


, while a large volume of air flows into the frame


34


via the second suction ports


37


, located beneath the cooling platen


27


.




Further, the portion of the printed recording medium P between the sheet feed roller


25


and the discharge roller


28


is maintained in close contact with the convex curved surface of the cooling platen


27


because of the urging force of the coil springs


33


as shown in FIG.


6


(


b


). Therefore, the underside surface of the recording medium P can be pressed entirely against the cooling platen


27


. Accordingly, it is possible to achieve highly effective heat transfer from the recording medium P to the cooling platen


27


to expedite the cooling of the recording medium P.




The large volume of air drawn into the frame


34


through the second suction ports


37


rapidly reduces the temperature of the cooling platen


27


, allowing the cooling platen


27


to quickly absorb heat from the recording medium P, which contacts the surface of the cooling platen


27


as the recording medium P is being discharged. Therefore, the hot-melt ink fixed to the recording medium P easily solidifies while being conveyed to the discharge section and before the inked portion being nipped between the discharge roller


28


and pinch roller


28




a


. The hot-melt ink solidifies before reaching this discharge section even if a path length up to the discharge roller is relatively short, and even when the printing speed is increased and the recording medium P is conveyed rapidly in the feeding direction. Accordingly, the freshly printed hot-melt ink is not transferred to the pinch roller


28




a


, and the quality of the printing can be maintained even in the high speed printing operation.




The adiabatic partition plate


38


disposed in the first suction port


36


serves to block heat radiated from the main platen


26


, which must be maintained at a high temperature, and to prevent the heat from transferring to the cooling platen


27


to thus allow the cooling platen


27


to be reliably maintained at a low temperature.




In the present embodiment, when printing on normal paper, the surface temperature of the main platen


26


is set at 68° C. for a resolution of 300 dpi and 65° C. for a resolution of 600 dpi. When printing on transparent film for overhead projectors, the surface temperature of the main platen


26


is set to 80° C. for 600 dpi. Accordingly, when it is necessary to change the type of recording medium P or printing conditions, the temperature of the main platen


26


during printing operations must be quickly adjusted.




For example, when modifying one of the above conditions, particularly when the temperature of the main platen


26


must be rapidly reduced, it is necessary to increase the cooling effect on the main platen


26


by air drawn in through the first suction port


36


. To accomplish this, the revolutions of the cooling fan


35


are increased with a state where the first suction port


36


is not blocked by the recording medium P, and the adiabatic partition plate


38


is provided in the first suction port


36


. This configuration increases the velocity of air flowing through the narrow channel formed between the downstream end of the main platen


26


and the adiabatic partition plate


38


, thereby increasing the cooling effect on the main platen


26


. This cooling effect can be further improved by forming the gap between the main platen


26


and the adiabatic partition plate


38


in a nozzle-like shape with a narrow inlet and a wide outlet leading toward the interior of the frame


34


.




In the-depicted embodiment, since the suction ports


36


and


37


are positioned downstream of the main platen


26


in the sheet feeding direction, the main platen


26


is positioned at the leeward side of the cooling platen


27


with respect to the cooling air flowing direction. Accordingly, a heat released from the main platen


26


cannot be easily directed toward the cooling platen


27


but is urged toward the leeward side of the cooling platen


27


. Thus, the cooling platen


27


can be protected against heat from the main platen


26


, and consequently, the cooling platen


27


can be effectively cooled by the cooling air.




Further, because of the geometrical arrangement of the suction ports


36


and


37


, if the first suction port


36


is not blocked by the recording medium P, the cooling platen


27


can be effectively cooled by the air flowing through both the first and second suction ports


36


,


37


, and the preheat platen


24


and the main platen


26


can also be cooled by the air through the first suction port


36


. Therefore, temperature of the preheat platen


24


and the main platen


26


can be lowered or controlled depending on the kind of the recording medium and the printing condition. Thus, efficient printing process can result. During printing operation, the cooling platen can be effectively cooled by the air through the second suction port


37


. Taking the air flowing direction into consideration, by disposing the cooling fan


35


at a center portion of the frame


34


, the air flow at upstream of the cooling fan


35


is utilized effectively for cooling the cooling platen


27


and the heating platen


26


, and the air flow at downstream of the cooling fan


35


is utilized for cooling the power board


42


. Consequently, a compact device with efficient cooling results.




Next, control routine for providing a suitable heating temperature, a suitable cooling temperature, a suitable printing speed and a suitable discharge timing of the printed recording medium will be described.




To enable the cooling platen


27


to sufficiently cool printed medium even under conditions that tend to heat up the cooling platen


27


, such as consecutive printing and relatively high ambient temperatures, the cooling platen


27


needs to be formed in a certain size and length. For this reason, the ink jet printer itself must be large enough to hold the large cooling platen. Therefore, a printer capable of properly cooling the printed recording medium without increasing the size of the cooling platen is required.




To this effect, in accordance with one embodiment of a control routine shown in

FIG. 8

, the CPU


50


controls a timing of supply of the recording medium P from the sheet supply unit


2


or


3


to the print head


11


according to temperature of the cooling platen


27


detected by the temperature sensor


56


.





FIG. 8

shows a flowchart indicating the timing control. The routine is started when a printing execution command is inputted, for example, when new print data is received from the host computer (not shown) for printing a first sheet of recording medium P or when the discharge sensor


55


detects discharge of a previously printed recording medium P for performing a subsequent printing operation in response to this detection.




Input of such a printing execution commands indicates a standby state for sending a sheet supply command signal to the sheet supply system driver circuit


68


for starting drive of the sheet supply unit


2


or


3


. Therefore in S


1


, a sheet supply command for driving the sheet supply units


2


,


3


, that is, to rotate one of the sheet supply rollers


22




a


,


22




b


, is prepared for transmission to the sheet supply system driver circuit


68


. Next in S


2


, it is determined whether or not the temperature of the cooling platen


27


detected by the temperature sensor


56


is equal to or less than a second setting temperature TC2. The second setting temperature TC2 is prestored in the ROM


51


and is the upper maximum temperature, for example, 50° C., at which the cooling platen


27


can properly cool the printed recording medium P.




When temperature detected by the temperature sensor


56


is equal to or less than the second setting temperature TC2 (S


2


:YES), then in S


3


, the sheet supply command signal for driving the sheet supply unit


2


or


3


is transmitted to the sheet supply system driver circuit


68


so that one of the sheet supply rollers


22




a


,


22




b


is rotated to supply a recording medium P to the print head


11


. Next, the recording medium P is printed on by the print head


11


in S


4


and is discharged in S


5


, thereby ending this routine.




On the other hand, when the temperature of the cooling platen


27


exceeds the second setting temperature TC2 (S


2


:NO), then in S


6


, the transmission of the sheet supply command signal to the driver circuit


68


is suspended until the temperature of the cooling platen


27


cools to equal or less than the second setting temperature TC2. That is, the routine goes back to S


2


.




Such a control routine can be advantageously used under circumstances where the temperature of the cooling platen


27


tends to rise above the second setting temperature TC2, so that the cooling platen


27


can not sufficiently cool the printed recording medium P. Such circumstances include when the printer is used in a relatively high ambient temperature and/or when the printer is used to perform printing of consecutive sheets. When the temperature of the cooling platen


27


exceeds the second setting temperature TC2, the control routine represented by the flowchart of

FIG. 8

delays supply of recording medium P to the print head


11


until the temperature of the cooling platen


27


drops to a temperature not more than the second setting temperature TC2, whereby the cooling platen


27


can sufficiently cool the printed recording medium P. Accordingly, the recording medium P will always contact the cooled cooling platen


27


having temperature not more than the second setting temperature TC2 so that the cooling platen


27


can sufficiently cool the printed recording medium P. As a result, the recording medium P will always be properly cooled. For this reason, there is no need to increase the size or the length of the cooling platen


27


with efficient printing performance.




A control routine according to a first modification is shown in a flowchart of FIG.


9


. The first modification pertains to an improvement on the foregoing control routine in that the printed recording medium is maintained on the cooling platen


27


for a controlled period in accordance with the temperature of the cooling platen


27


, the temperature being detected by the temperature sensor


56


. In other words, the first modification further controls a timing of the discharge of the printed recording medium from the cooling platen


27


.




This routine starts in the same manner as the routine explained while referring to the flowchart of FIG.


8


. Further, the steps S


7


, S


8


and S


9


are identical with the steps S


1


, S


2


, S


3


, respectively, in the control routine shown in FIG.


8


.




When the temperature of the cooling platen


27


is equal to or less than the second setting temperature TC2 (S


8


:YES), then, in S


10


, it is determined whether or not the detected temperature of the cooling platen


27


is equal to or less than a first setting temperature TC1 of, for example, 45° C. When the detected temperature is not more than the first setting temperature TC1 (S


10


:YES), then in S


11


, one of the sheet supply units


2


or


3


is controlled to supply a recording medium P to the print head


11


. Next, in S


12


the recording medium P is printed on by the print head


11


.




Afterward, rather than immediately discharging the printed-on recording medium P by continuous rotation of the sheet feed roller


25


and the discharge roller


28


, instead, in S


13


the discharge operations are suspended while the lastly printed on portion of the recording medium P is held over the cooling platen


27


for a predetermined duration of time, which will be referred to as the first waiting time WT


1


, hereinafter. The first waiting time WT


1


is prestored in the ROM


51


and is set to a value of, for example, 300 msec. After the lastly printed portion of the recording medium P has been held over the cooling platen


27


for the first waiting time WT


1


, then in S


17


, the sheet feed roller


25


and the discharge roller


28


are driven to rotate to discharge the recording medium P. This ends the control routine of FIG.


9


.




On the other hand, if the temperature of the cooling platen


27


is not more than the second setting temperature TC2 (S


8


:YES) and also exceeds the first setting temperature TC1 (S


10


:NO), then in S


14


, one of the sheet supply units


2


or


3


supplies a recording medium P to the print head


11


, whereupon in S


15


the print head


11


prints on the recording medium P. After printing has been completed in S


15


, then in S


16


, the lastly printed portion of the recording medium P is held over the cooling platen


27


for a predetermined duration of time, which will be referred to as the second waiting time WT


2


, hereinafter. The second waiting time WT


2


is also prestored in the ROM


51


and is set to a duration of time, for example, 500 msec., that is longer than the first waiting time WT


1


. After the lastly printed portion of the recording medium P has been held over the cooling platen


27


for the second waiting time WT


2


, the recording medium P is discharged in S


17


and this control routine is ended.




In the first modified control routine, the control of discharge timing is added to the control of the sheet supply timing. Therefore, when the temperature of the cooling platen


27


is fairly low, so that the cooling platen


27


will be able to cool the recording medium P fairly rapidly, then the lastly printed portion of the recording medium P is held over the cooling platen


27


for only a relatively short time. On the other hand, when the temperature of the cooling platen


27


is fairly high, so that the cooling platen


27


requires a longer time to cool the recording medium P, then the lastly printed portion of the print medium P is held over the .-!Lo cooling platen


27


for a relatively long time. As a result, the lastly printed portion of the recording medium P can be held over the cooling platen


27


for an optimum duration of time corresponding to the temperature of the cooling platen


27


. By the control process including the discharge timing control, the recording medium can be more efficiently cooled. Accordingly, efficiency of printing operations can be improved.




A control routine according to a second modification is shown in a flowchart of FIG.


10


. The second modification pertains to a control to the temperature of the heating platen (preheat platen


24


and the main platen


26


) in accordance with the temperature of the cooling platen


27


. In this control the temperatures of the preheat platen


24


and the main platen


26


are detected by pre-thermistor


69


and the main thermistor


70


, respectively, and the temperature of the cooling platen


27


is detected by the temperature sensor


56


.




This routine starts in the same manner as the routine explained while referring to the flowchart of FIG.


8


. Further, steps S


18


, S


19


, and S


20


are identical with the steps S


1


, S


2


and S


6


of

FIG. 8

or with the steps S


7


, S


8


and S


9


of FIG.


9


. If the temperature of the cooling platen


27


is equal to or less than the second setting temperature TC2 (S


19


:YES), then in S


21


, it is determined whether or not the temperature of the cooling platen


27


is equal to or less than the first setting temperature TC1, which is the same as the step S


10


in FIG.


9


. When the temperature of the cooling platen


27


is equal to or less than the first setting temperature TC2 (S


21


:YES), then in S


22


, the temperature of the heating platens


24


,


26


are controlled to match a first heating temperature TP1. The first heating temperature TP1 is prestored in the ROM


51


and is set to, for example, 68° C. When the temperature of the cooling platen


27


is equal to or less than the second setting temperature TC2 (S


19


:YES) and also exceeds the first setting temperature TC1 (S


21


:NO), then a routine goes into step S


23


having steps S


23


-


1


, S


23


-


2


and S


23


-


3


for controlling the temperature of the heating platens to a second heating temperature TP2 which is also prestored in the ROM


51


and is set to a temperature lower than the first heating temperature TP1, that is, for example TP2=60° C.




More specifically, in step S


23


-


1


, the CPU


50


transmits command signal to the fan driver circuit


65


so as to rotate the cooling fan


35


at a higher speed in order to cool the heating platens


24


,


26


. Then, in step S


23


-


2


, judgment is made as to whether or not the temperature of the heating platens


24


,


26


becomes not more than a second heating temperature TP2. If the judgment falls No, the routine returns back to S


23


-


1


to continue fan-cooling. On the other hand, if the temperature of the cooling platens becomes not more than the second heating temperature TP2, the routine proceeds into S


23


-


3


where a control is made to maintain the temperature of the heating platens


24


,


26


at the second heating temperature TP2.




After either of S


22


and S


23


-


3


are performed, then in S


24


, the recording medium P is supplied from one of the sheet supply units


2


,


3


to the print head


11


. The recording medium P is printed on by the print head


11


in S


25


, and then is discharged from the printer in S


26


. This ends the control routine represented by the flowchart in FIG.


10


.




In the second modification, the control of the temperature of the heating platens


24


,


26


is preformed in addition to the sheet supply timing control. For example, when the temperature of the cooling platen


27


is equal to or less than 45° C.(TC1), the temperature of the heating platens


24


,


26


can be controlled to 68° C.(TP1). When the temperature of the cooling platen


27


exceeds 45° C.(TC1) and is also equal to or less than 50° C. (TC2), then the temperature of the heating platens


24


,


26


can be controlled to 60° C. (TP2).




Said differently, when the temperature of the cooling platen is fairly low, then the temperature of the heating platens


24


,


26


is increased so that ink can be more reliably fixed on the print medium P. On the other hand, when the temperature of the cooling platen


27


is fairly high, then the temperature of the heating platen


24


,


26


can be lowered to a temperature which increases cooling efficiency of the cooling platen


27


, but which does not adversely affect the fixation strength of ink. Accordingly, control operations can be refined and efficiency of print operations can be improved.




It should be noted that the control operations for controlling temperature of the heating platen


24


,


26


are performed based on temperatures detected by the pre thermistor


69


and main thermistor


70


for the preheat platen


24


and the main platen


26


. Based on the detected temperatures, a control command is transmitted from the CPU


50


to the heater control circuit


64


to heat the heating platens


24


,


26


to the predetermined temperatures TP1, TP2. Further, the control command is also transmitted from the CPU


50


to the fan driver circuit


65


to cool the heating platen as in the step S


23


-


1


.




A control routine according to a third modification is shown in a flowchart of FIG.


11


. The third modification pertains to a control to print speed of the nozzle head


13


according to the temperature detected for the cooling platen


27


by the temperature sensor


56


in addition to the control to the sheet supply timing toward the nozzle head


13


.




In the routine of

FIG. 11

, the start timing and steps S


27


through S


30


are identical with the start timing and the steps S


18


through S


21


of FIG.


10


. In the step S


30


, if the detected temperature of the cooling platen


27


is not more than the first setting temperature TC1 (S


30


:YES), then in S


31


, the print speed of the nozzle head


13


is controlled to a first print speed PS


1


. The first print speed PS


1


is prestored in the ROM


51


and is set to, for example, 26.7 inches per second (ips).




On the other hand, if the temperature of the cooling platen


27


is determined to be not more than the second setting temperature TC2 (S


28


:YES) and to have exceeded the first setting temperature TC1 (S


30


:NO), then the routine proceeds into S


32


where the print speed of the nozzle head


13


is controlled to a second print speed PS


2


. The second print speed PS


2


is also provisionally stored in the ROM


51


and is set to a speed, for example, 13.4 ips, that is slower than the first print speed PS


1


.




Next, in S


33


a recording medium P is supplied from one of the sheet supply units


2


,


3


. In S


34


, the print head


11


prints on the supplied recording medium P at print speed designated in S


31


or S


32


. Afterward, the printed-on recording medium P is discharged in S


35


, thereby ending this control operation.




With this control routine, if the temperature of the cooling platen


27


is fairly low, so that the recording medium P can be quickly cooled, then printing can be performed at a fairly high speed so that printing operations can be quickly performed. On the other hand, if the temperature of the cooling platen


27


is fairly high, then the print speed of the nozzle head


13


is slowed down so that the recording medium P remains over the cooling platen


23


for a longer period of time to enhance cooling effects of the cooling platen


23


. Because the recording medium P contacts the cooling platen


27


for a longer period of time, the recording medium P can be properly cooled. Therefore, cooling can be efficiently performed and efficiency of print operations can be improved.




It should be noted that during operations for controlling print speed of the nozzle head


13


, the CPU


50


transmits signals to the carriage driver circuit


63


and the print head driver circuit


62


in order to drive the nozzle head


13


and the carriage motor


60


so that one band at a time is printed. Also, the CPU


50


transmits signals to the feed system driver circuit


66


in order to intermittently drive the sheet feed roller


25


and the discharge roller


28


by a predetermined feed amount. By doing this, portions of the recording medium P printed on one band amount at a time can be consecutively fed to the cooling platen


27


.




While the invention has been described in detail and with reference to the specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.




For example, a gap is provided between the main platen


26


and the cooling platen


27


and the gap is plugged with an adiabatic member in order to prevent thermal transfer from the main platen


26


to the cooling platen


27


. With this arrangement, the first suction port


36


is plugged by the adiabatic plug. However, it is also possible to provide cooling port(s) below the cooling platen


27


(equivalent to the second suction ports


37


shown in FIG.


4


). With this construction, the cooling platen


27


can be reliably maintained at a low temperature by air passing through the second suction ports


37


, whether during a printing operation or during a standby state, regardless of the position of the recording medium P being transferred. Alternatively, a first suction port can be formed in the adiabatic plug.




In the embodiment described above, the first suction port


36


is provided between the main platen


26


and cooling platen


27


. However, the second suction ports


37


can be omitted. In place of the second suction ports


37


, it is possible to provide other suction openings (not shown) in the frame


34


or the like. With this construction, it is possible to achieve temperature changes (temperature reductions) of the main platen


26


and the cooling function of the cooling platen


27


when the first suction port


36


is not blocked by the recording medium P, similar to the embodiment described above. Also, when the first suction port


36


is blocked by the recording medium P, it is possible to easily perform constant cooling of the power board


42


using air introduced into the frame


34


from the other suction openings.




Further, in the embodiment described above, the preheat platen


24


contacts the underside surface of the recording medium P, as does the main platen


26


, in order to a


5


. preheat the recording medium P. However, it is not necessary for the preheat platen


24


to contact the underside surface of the recording medium P. For example, the preheat platen


24


can be provided to contact the top surface of the recording medium P (the surface on which ink is to be fixed), or two preheat platens could be provided in two places contacting both the top and underside surfaces of the recording medium P. A concave curved preheat platen provided to contact the top surface of the recording medium P could be particularly effective for heating the surface on which ink is to be fixed.




Further, the preheat platen


24


does not necessarily need to be as wide as or wider than the recording medium P. For example, if the material used for the recording medium P has some degree of thermal conductivity, a preheat platen slightly smaller than the recording medium P in the main scanning direction or provided in contact with the recording medium P in intervals in the widthwise direction would be sufficiently effective for preheating.




Further, various control routines are conceivable other than those described with reference to

FIGS. 8 through 11

. That is, in the illustrated embodiments, (a) control of the timing of the supply of the recording medium P to the print head


11


in accordance with the temperature of the cooling platen is performed (FIG.


8


), and one of the (b) control of staying period of the printed recording medium on the cooling platen (FIG.


9


), (c) control of the temperature of the heating platens


24


,


26


(

FIG. 10

) and (d) control of the printing speed at the nozzle head


13


(

FIG. 11

) in accordance with the temperature of the cooling platen is added to the supply timing control(a). However, various combination among the controls (b) through (d) can be added to the control (a). Further, various combination among the controls (a) through (d) is available.




Further, the above described controls (a) through (d) are well-suited for the hot-melt type ink jet printers. However, these controls can be used appropriately with other types of printers as well.



Claims
  • 1. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding direction along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a sheet discharge opening adjacent the discharge roller, an order of the main platen, the cooling platen and the discharge roller defining a sheet feed passage, wherein the frame is formed with a suction port at a position downstream of the main platen, the printer further comprises a fan disposed in the frame and positioned at a side facing the opposite surfaces of the main platen and the cooling platen, the fan introducing a cooling air into the frame through the sheet discharge opening and directing the cooling air toward the cooling platen through the suction port to cool the cooling platen, and the suction port includes a first suction port positioned between the main platen and the cooling platen at an upstream side of the cooling platen and open to the sheet feed passage so that the first suction port is closed by the image receiving medium when the image receiving medium passes along the sheet feed passage, and the hot-melt type ink jet printer further comprises an adiabatic partition member positioned in the first suction port for adiabatically separating the main platen from the cooling platen.
  • 2. The hot-melt type ink Jet printer as claimed in claim 1, wherein the frame has a front side at which a printed image receiving medium is discharged, and a rear side at which the image receiving medium is supplied into the sheet feed passage, the fan being positioned at an intermediate portion between the front side and the rear side;and the hot-melt type ink jet printer further comprising a power board positioned between the fan and the rear side of the frame, so that the cooling air sucked by the fan into the frame through the suction port is applied to the power board.
  • 3. The hot-melt type ink jet printer as claimed in claim 1, wherein the image receiving medium has a first surface and a second surface opposite the first surface, the first surface being in confrontation with the nozzle head, and the second surface being in confrontation with the one surfaces of the main platen and the cooling platen;and wherein the hot-melt type ink jet printer further comprising a main heater provided at the opposite surface of the main platen.
  • 4. The hot-melt type ink jet printer as claimed in claim 1, wherein the suction port further includes a second suction port disposed downstream of the cooling platen and positioned offset from the sheet feed passage for supplying the cooling air toward the opposite surface of the cooling platen.
  • 5. The hot-melt type ink jet printer as claimed in claim 2, further comprising a cooling fin provided at the opposite surface of the cooling platen and positioned in confrontation with the suction port.
  • 6. The hot-melt type ink jet printer as claimed in claim 1, further comprising a control unit connected to the fan for controlling a rotation speed of the fan so that the fan rotates at a first speed during printing operation and at a second speed lower than the first speed during a standby state.
  • 7. The hot-melt type ink Jet printer as claimed in claim 1, wherein the frame comprises a support frame supporting portions of the opposite surfaces of the main platen and the cooling platen, the support frame being formed with an air introduction port for allowing the cooling air sucked into the frame through the suction port to be directed toward the fan.
  • 8. The hot-melt type ink jet printer as claimed in claim 2, wherein the frame comprises a support frame supporting portions of the opposite surfaces of the main platen and the cooling platen, the support frame being formed with an air introduction port for allowing the cooling air sucked into the frame through the suction port to be directed toward the fan.
  • 9. The hot-melt type ink jet printer as claimed in claim 2, wherein the suction port includes a first suction port provided at a position between the main platen and the cooling platen, and a second suction port disposed at a downstream of the cooling platen.
  • 10. The hot-melt type ink jet printer as claimed in claim 2, further comprising an adiabatic partition member positioned in the first suction port for adiabatically separating the main platen from the cooling platen, and wherein the rear side of the frame is formed with a discharge port through which the cooling air passing through the power board is discharged to an outside.
  • 11. The hot-melt type ink jet printer as claimed in claim 2, further comprising a control unit connected to the fan for controlling a rotation speed of the fan so that the fan rotates at a first speed during printing operation and at a second speed lower than the first speed during a standby state.
  • 12. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding direction along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; and a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a sheet discharge opening adjacent the discharge roller, an order of the main platen, the cooling platen and the discharge roller defining a sheet feed passage, wherein a combination of the nozzle head and the main platen constitutes a printing portion, and the hot-melt type ink jet printer further comprising: a temperature sensor provided downstream of the printing portion detecting a temperature of the cooling platen; and means for controlling a printing speed of the nozzle head in accordance with a temperature detected by the temperature sensor.
  • 13. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding direction along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; and a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a sheet discharge opening adjacent the discharge roller, an order of the main platen, the cooling platen and the discharge roller defining a sheet feed passage, wherein a combination of the nozzle head and the main platen constitutes a printing portion, and the hot-melt type ink jet printer further comprising: a preheat platen provided between the sheet supplying section and the main platen; a temperature sensor provided downstream of the printing portion detecting a temperature of the cooling platen; and means for controlling a temperature of the preheat platen in accordance with a temperature detected by the temperature sensor.
  • 14. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding directing along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a discharge port adjacent the discharge roller, an order of the main platen, the cooling platen and the discharge roller defining a sheet feed passage; a sheet supplying section storing a stack of the image receiving mediums and having a sheet supply opening for supplying each one of the image receiving mediums of the stack; a sheet feed roller disposed downstream of the sheet supplying section and upstream of the cooling platen, a combination of the sheet supply opening, the main platen, the sheet feed roller, the cooling platen and the discharge roller defining an arcuate sheet feed passage protruding toward the nozzle head; and an urging segment connected between the cooling platen and the frame for urging the cooling platen toward the nozzle head so that the one surface of the cooling platen is discontinuous from the arcuate sheet feed passage.
  • 15. The hot-melt type ink jet printer as claimed in claim 14, further comprising:a preheat platen positioned between the sheet supply opening and the sheet feed roller, the preheat platen having one surface and opposite surface; a preheater provided at the opposite surface of the preheat platen; a main heater provided at the opposite surface of the main platen, and wherein the main platen is positioned downstream of the sheet feed roller, each one surface of the preheater, main heater and the cooling platen being arcuately curved.
  • 16. The hot-melt type ink jet printer as claimed in claim 14, wherein the urging segment provides a biasing force that yields the one surface of the cooling platen to be in conformance with the arcuate sheet feed passage by a tension of the image receiving medium the tension being imparted by the sheet feed roller and the discharge roller.
  • 17. The hot-melt type ink jet printer as claimed in claim 15, further comprising at least one baffle having a free end urged toward at least one of one surfaces of the preheat platen and the main platen for pressing the image receiving medium on the one surface.
  • 18. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding direction along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; and a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a sheet discharge opening adjacent the discharge roller, an order of the main platen, the cooling platen and the discharge roller defining a sheet feed passage, wherein a combination of the nozzle head and the main platen constitutes a printing portion, and the hot-melt type ink jet printer further comprising: a sheet supplying section for supplying each one of the image receiving mediums to the printing portion; a temperature sensor provided downstream of the printing portion detecting a temperature of the cooling platen; and means for controlling a supplying timing of the image receiving medium from the sheet supplying section in accordance with a temperature detected by the temperature sensor.
  • 19. The hot-melt type ink jet printer as claimed in claim 18, further comprising means for temporarily stopping a printed image receiving medium upon the cooling platen for a selected period in accordance with a temperature detected by the temperature sensor.
  • 20. The hot-melt type ink jet printer as claimed in claim 18, further comprising means for controlling a temperature of the main platen in accordance with a temperature detected by the temperature sensor.
  • 21. The hot-melt type ink jet printer as claimed in claim 18, further comprisinga preheat platen provided between the sheet supplying section and the main platen; and means for controlling a temperature of the preheat platen in accordance with a temperature detected by the temperature sensor.
  • 22. The hot-melt type ink jet printer as claimed in claim 18, further comprising means for controlling a printing speed of the nozzle head in accordance with a temperature detected by the temperature sensor.
  • 23. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding direction along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; and a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a sheet discharge opening adjacent the discharge roller, an order of the main platen the cooling platen and the discharge roller defining a sheet feed passage, wherein a combination of the nozzle head and the main platen constitutes a printing portion, and the hot-melt type ink jet printer further comprising: a temperature sensor provided downstream of the printing portion detecting a temperature of the cooling platen; and means for temporarily stopping a printed image receiving medium upon the cooling platen for a selected period in accordance with a temperature detected by the temperature sensor.
  • 24. A hot-melt type ink jet printer for forming an inked image on an image receiving medium comprising:a frame; a nozzle head ejecting a hot-melt ink onto the image receiving medium; a main platen having one surface in confrontation with the nozzle head, the image receiving medium being fed in a feeding direction along the one surface, the main platen having an opposite surface; a cooling platen positioned downstream of the main platen in the feeding direction for cooling the inked image formed on the image receiving medium, the cooling platen having one and opposite surfaces; and a discharge roller disposed downstream of the cooling platen for discharging the image receiving medium, the frame having a sheet discharge opening adjacent the discharge roller, an order of the main platen, the cooling platen and the discharge roller defining a sheet feed passage, wherein a combination of the nozzle head and the main platen constitutes a printing portion, and the hot-melt type ink jet printer further comprising: a temperature sensor provided downstream of the printing portion detecting a temperature of the cooling platen; and means for controlling a temperature of the main platen in accordance with a temperature detected by the temperature sensor.
Priority Claims (4)
Number Date Country Kind
9-171997 Jun 1997 JP
9-171998 Jun 1997 JP
9-176917 Jul 1997 JP
9-192594 Jul 1997 JP
US Referenced Citations (6)
Number Name Date Kind
4664542 Tsugita May 1987
5005025 Miyakawa et al. Apr 1991
5043741 Spehrley, Jr. Aug 1991
5406316 Schwiebert et al. Apr 1995
5774155 Median et al. Jun 1998
5847719 Yamaguchi et al. Dec 1998
Foreign Referenced Citations (3)
Number Date Country
3-58853 Mar 1991 JP
5-131620 May 1993 JP
2575136 Oct 1996 JP