Device for cooling thermal head

Abstract: A device for cooling a thermal head (1) of a thermal image recording apparatus comprising a ventilation unit (5) for producing a stream of air for cooling the thermal head (1) and a duct (9) for guiding the stream of air having cooled the thermal head (1) outside the recording apparatus. The air heated by having cooled the thermal head (1) does not circulate within the recording apparatus, whereby the temperature within the recording apparatus can be prevented from rising.

Description: BACKGROUND OF THE INVENTION The present invention relates to a device for cooling a thermal head arranged within a thermal image recording apparatus. Fig. 3 is a perspective view showing the main portion of a conventional device for cooling a thermal head disclosed, e. g., in Japanese Patent Application (UPA) No. 147374/1985 (the term "UPA" as used herein means "Unexamined published Application"). In the figure, reference numeral (1) designates a thermal head; (2), a radiating fin mounted on the thermal head (1); (3), a platen roller; (4), a sheet of image recording paper; (5), a blower; (6) a conduit for guiding a stream of air from the blower (5); and (7), a slot, arranged on the conduit (6), for blowing out the stream of air. An operation of the conventional device for cooling a thermal head as constructed above will be described. In a thermal image recording apparatus, a predetermined image is recorded on the image recording sheet (4) by heat generated by an electric signal applied to heating elements of the thermal head (1). The amount of formation of picture elements of the image depends on such factors as the temperature of the heating elements, i. e., the amount of electric energy applied to the heating elements and the temperature of the thermal head (1) itself. The electric energy applied to the heating elements is controlled within a prescribed value by a control circuit. The thermal head (1), on the other hand, keeps the temperature from rising by dissipating the heat stored by printing from the radiating fin (2). Also, the stream of air produced by the blower (5) is blown to the radiating fin (2) from the slot (7) to improve the radiating efficiency of the radiating fin (2) and to make the temperature distribution of the thermal head (1) uniform. Generally, the conventional device for cooling a thermal head is accommodated within a case that constitutes the image recording apparatus. Since the device for cooling a thermal head is constructed as described above, the air blown from the blower (5) to the radiating fin (2) and thus heated by going through the radiating fin (2) circulates within the case of the image recording apparatus, thereby increasing the temperature inside the image recording apparatus. Hence, the thermal head (1) is also heated, and as a result, the problem that the increase in temperature within the image recording apparatus reduces the life of various parts, especially, of electric components, constituting the image recording apparatus. From JP-A-60/49 986 a thermal transfer type image forming device is known which includes a blowing fan for cooling the thermal head. The blowing fan is placed in a duct connected to one end of the thermal head. Air is sucked by the fan and passed through a heat radiating plate to cool the thermal head and then exhausted from the duct. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problem and has as an object the provision of a device for cooling a thermal head such that an increase of the internal temperature of a thermal image recording apparatus is avoided. According to the present invention this object is solved by a device for cooling a thermal head arranged within a thermal recording apparatus having a case, comprising: ventilation means for producing a stream of air for cooling said thermal head; and a duct means for guiding the stream of air after having cooled said thermal head; characterized in that one opening of said duct guiding the stream of air is located confronting a ventilation hole disposed at a predetermined position in the case. The device for cooling a thermal head according to the present invention is operated so that the duct guides the heated air to the outside of the image recording apparatus. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing the main portion of an embodiment of the present invention; Fig. 2 is a sectional view taken along line A-A of Fig. 1; and Fig. 3 is a perspective view showing the main portion of a conventional device for cooling a thermal head. DETAILED DESCRIPTION OF THE PREFERED EMBODIMENT Fig. 1 is a perspective view showing the main portion of an embodiment of the present invention, and Fig. 2 is a sectional view taken along line A-A of Fig. 1. In the figures, reference numerals (1) through (5) designate the parts and components as the conventional example. Reference numeral (8) designates a case of the image recording apparatus; (8a), a ventilating hole disposed at a predetermined position on a lateral side of the case (8); and (9), a duct, one opening of which is located confronting the ventilating hole (8a). This opening is provided with the blower (5) serving as ventilation means for discharging air form the inside of the duct (9) to the outside of the image recording apparatus through the ventilating hole (8a). The other opening of the duct (9) is arranged so as to face the radiating fin (2). Reference numeral (10) designates a cover which covers the projecting ribs of the radiating fin (2) and has an air collecting hole (10a) for collecting air that passes through the ribs substantially at the middle thereof; (11), an expander elastically connecting between the periphery of the air collecting hole (10a) and that of the other opening of the duct (9) and shielding the interior of the image recording apparatus; (12), a hook for holding the other opening of the duct (9) and the radiating fin (2) through the cover (10) and the expander (11); (13), an ink sheet for thermal transfer; (14), a compression spring; (15), an arm which is pivotally supported by a shaft (16) so as to hold the thermal head (1) and the radiating fin (2). This arm can separate the thermal head (1) from the platen roller (3) with the shaft (16) as a pivot. Since the other opening of the duct (9) is also pivotally supported by the shaft (16), the duct (9) is rotated in synchronism with the thermal head (1) when the thermal head (1) is separated from the platen roller (3). In the device for cooling a thermal head thus constructed, the steam of air is generated by the blower (5) and flows from reference character B to reference character C in the figures. This air stream cools the thermal head (1) through the radiating fin (2) and the air heated by the cooling of the fin (2) is discharged outside the image recording apparatus through the expander (11), duct (9), and the ventilating hole (8a). Thus, the air heated by cooling the thermal head (1) does not circulate within the image recording apparatus, whereby increase in temperature within the image recording apparatus can be prevented. As described above, the present invention can provide a device for cooling a thermal head by which air that has cooled the thermal head through the radiating fin does not increase the temperature within the image recording apparatus with its ventilation means for producing a stream of air for cooling the radiating fin and its duct for guiding the air stream after cooling the radiating fin outside the image recording apparatus. While there has been descrited in connection with the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claims all such changes and modifications as fall within the scope of the invention.

Claims: A device for cooling a thermal head (1) arranged within a thermal recording apparatus having a case (8), comprising: ventilation means (5) for producing a stream of air for cooling said thermal head (1); and a duct means (9) for guiding the stream of air after having cooled said thermal head (1); characterized in that one opening of said duct (9) guiding the stream of air is located confronting a ventilation hole (8a) disposed at a predetermined position in the case (8). A device according to claim 1, characterized in that said opening of said duct (9) is provided with a blower (5) for discharging air from the inside of the duct (9) to the outside of the image recording apparatus. A device according to claim 1 or 2, characterized by a cover (10) covering projecting ribs of a radiating fin (2) of said thermal head (1); said cover (10) having an air collection hole (10a) for collecting air that passes through the ribs, and an expander (11) elastically connecting between the periphery of the air collecting hole (10a) and said duct (9).

Inventors: UNE RYUZO C O MITSUBISHI DENKI, UNE, RYUZO, C/O MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1990
Main classification: B41J29
IPC codes: B41J29