Heat transfer device for sheet assembly

A heat transfer device for sheet assembly for the heat transfer of an image on a transfer sheet to a receptor sheet for printing by inserting a sheet assembly comprising the transfer sheet on which an image has been formed and a receptor sheet for printing superimposed on an auxiliary plate into an inlet opening portion formed on a casing along an inlet stand, and passing between a pair of heat pressure rolls arranged inside the casing, includes: an exhaust fan for taking the outside air from the inlet opening portion toward the pair of the heat pressure rollers for cooling the pair of the heat pressure rollers; and aperture maintaining means for maintaining air passage for allowing the intake of the outside air between the upper edge portion of the inlet opening portion and the upper surface of the sheet assembly at the time of inserting the sheet assembly into the inlet opening portion. Accordingly, the pair of the heat pressure rollers can be securely cooled by the outside air via the air passage.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
The present invention relates to a heat transfer device for sheet assembly 
or a laminator, wherein the sheet assembly comprising a transfer sheet on 
which an image has been formed and a receptor sheet for printing 
superimposed on an auxiliary plate passes between a pair of heat pressure 
rollers so as to heat transfer the image on the transfer sheet onto the 
receptor sheet for printing. 
2. Description of the Related Art 
When an image is digitally processed and the image is transferred onto a 
transfer sheet with a printer based on the digital data, an image with a 
rich tone can be reproduced, realizing a sharp image quality. Since the 
tone of the image obtained a printed matter obtained by the offset 
printing of the image on the transfer sheet is slightly different from the 
tone of the image on the transfer sheet, a printing sample applied with 
color correction beforehand is necessary in order to grasp the finished 
image on the printed matter accurately. 
As a device for producing the printing sample, recent attention is paid to 
a heat transfer device for sheet assembly (laminator). The heat transfer 
device for sheet assembly is constructed to transfer an image on a 
transfer sheet 100 onto a receptor sheet for printing by inserting a sheet 
assembly 108 comprising a transfer sheet 100 on which an image has been 
formed and a receptor sheet for printing 102 superimposed on an auxiliary 
plate 104 of an aluminum plate of about 0.3 mm thickness, further applied 
with a cover sheet 106 thereon, from an inlet opening formed on a casing 
along an inlet stand, and passing between a pair of heat pressure rollers. 
By the use of an ink ribbon applied with a thin film containing a pigment 
matched with the hue of a printing ink for printing an image on a transfer 
sheet based on digital data, a printing sample excellently exact to the 
actual printed matter at the time of the heat transfer of the image on the 
transfer sheet on the receptor sheet for printing can be provided stably. 
In the heat transfer device for sheet assembly, the pair of heat pressure 
rolls comprise soft rollers comprising core rollers of metal pipes, of 
which surface covered with a soft synthetic resin such as silicone rubber, 
and built-inheat lamps. In order to obtain a printing sample exact to the 
actual printed matter, it is necessary to have the temperature of the heat 
pressure rollers homogeneously as much as possible at the time of the heat 
transfer by pressing the transfer sheet onto the receptor sheet for 
printing with the heat pressure rollers. If the temperature of the heat 
pressure rollers rises during the heat transfer process, not only 
inconveniences occur such as uneven transfer and generation of wrinkles in 
the receptor sheet for printing due to difficulty of peeling off the 
transfer sheet and the receptor sheet for printing, but also deterioration 
of the heat pressure rollers due to the temperature higher than the 
bearable temperature of the soft synthetic resin. 
Therefore, the temperature of the heat pressure rollers is measured by a 
sensor for thyristor control of the power inputted to the heater lamps 
arranged in the heat pressure rollers. In order to prevent casting heat 
effect on other electric control parts in the casing, the temperature rise 
of the heat pressure rollers is prevented by covering the heat pressure 
rollers with roller covers as well as providing an exhaust fan at the 
bottom of the casing for taking cooling air from the inlet opening and 
cooling the heat pressure rollers. 
Since the transfer sheet and the receptor sheet for printing adsorb 
moisture, the moisture may be evaporated by the heat of the heat pressure 
rollers so that the sheet assembly curls at the time of inputting from the 
inlet opening formed on the casing along the inlet stand. As to the 
auxiliary plate, even though it comprises an aluminum plate, in the case 
the thickness is about 0.3 mm, "warpage" would generate over a long term 
use. Accordingly, the sheet assembly may contact to the upper edge or 
surface of the inlet opening and choke the inlet opening due to 
deformation. In this case, intake of the cooling air from the inlet 
opening is bothered, resulting in extraordinary temperature rise of the 
heat pressure rollers. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a heat 
transfer device for sheet assembly without the risk of completely choking 
the inlet opening, which is the intake opening of the cooling air with a 
deformed sheet assembly at the time of inserting the sheet assembly from 
the inlet opening formed on the casing along the inlet stand so that the 
temperature rise of the heat pressure rollers is prevented. 
In order to achieve the above-mentioned object, a first aspect of the 
present invention is a heat transfer device for sheet assembly for heat 
transfer of an image on a transfer sheet to a receptor sheet for printing 
by inserting a sheet assembly comprising the transfer sheet on which an 
image has been formed and a receptor sheet for printing superimposed on an 
auxiliary plate into an inlet opening portion formed on a casing along an 
inlet stand, and passing between a pair of heat pressure rolls arranged 
inside the casing, comprising: 
an exhaust fan for taking the outside air from the inlet opening portion 
toward the pair of the heat pressure rollers for cooling the pair of the 
heat pressure rollers; and 
an air passage maintaining means for maintaining the air passage for 
allowing the intake of the outside air between the upper edge portion of 
the input opening portion and the upper surface of the sheet assembly at 
the time of inserting the sheet assembly into the inlet opening portion. 
According to this aspect, since the air passage is maintained between the 
upper edge portion of the inlet opening portion and the upper surface of 
the sheet assembly even if the sheet assembly is deformed, the intake of 
the outside air by the exhaust fan toward the pair of the heat pressure 
rollers is ensured. 
A second aspect comprises a protruding portion extending toward the pair of 
the heat pressure rollers from the inlet opening portion as the air 
passage maintaining means in the first aspect. 
A third aspect comprises the protruding portion provided in a plurality 
along the transverse direction of the inlet opening portion in the second 
aspect. 
In a fourth aspect, the pair of the heat pressure rollers are covered with 
a cover member comprising openings for allowing passage of the sheet 
assembly along the conveyance direction of the sheet assembly, with the 
cover member provided with a guiding means for guiding the air inside the 
cover member to the exhaust fan direction in the first aspect. 
In a fifth aspect, the exhaust fan is arranged on one side with respect to 
the conveyance direction of the sheet assembly, and the guiding means 
comprises a limiting member for limiting discharge of the air inside the 
cover member to the other side with respect to the conveyance direction of 
the sheet assembly in the first aspect. 
In a sixth aspect, the guiding means comprises a promoting portion for 
promoting the discharge of the air inside the cover member to the one side 
with respect to the conveyance direction of the sheet assembly in the 
fifth aspect. 
A seventh aspect further comprises a housing having the inlet opening 
portion and an outlet opening portion for discharging the sheet assembly 
inserted from the inlet opening portion, with a part of the housing in the 
vicinity of the outlet opening portion at the other side with respect to 
the conveyance direction of the sheet assembly providing an inflow 
preventing portion of the outside air.

DESCRIPTION OF THE EMBODIMENT 
Hereinafter an embodiment of the present invention will be explained in 
detail with reference to drawings. As shown in FIGS. 1 and 5, a sheet 
heating device or laminator 90 comprises a substantially 
rectangular-shaped casing or hausing 10. The casing 10 is provided with an 
inlet stand 11 and an outlet stand 13 at the both sides. An inlet opening 
12 is formed on the casing 10 along the inlet stand 11, and an outlet 
opening 14 is formed on the casing 10 along the outlet stand 13. 
Furthermore, guiding means 60, 61, and 62 are successively provided at the 
same level as that of the inlet stand 11 and the outlet stand 13 in the 
casing 10 along the conveyance direction of a sheet assembly 108 shown in 
FIG. 6. The guiding means 60 comprises a lower guiding plate 60A and an 
upper guiding plate 60B, the guiding means 61 comprises a lower guiding 
plate 61A and an upper guiding plate 61B, and the guiding means 62 
comprises a lower guiding plate 62A and an upper guiding plate 62B. 
A pair of heat pressure rollers 20 and 20 are provided rotatably and 
vertically, contacted to each other with pressure between the guiding 
means 60 and the guiding means 61. A pair of discharge rollers 30 and 30 
are provided rotatably and vertically, contacted to each other with 
pressure between the guiding means 61 and the guiding means 62. The heat 
pressure rollers 20 and the discharge rollers 30 are rotated by a chain 41 
wound around sprockets on the output shaft of a driving motor 40 to the 
directions shown with arrows synchronically. 
The heat pressure rollers 20 and the discharge rollers 30 comprise soft 
rollers comprising metal pipes, of which surface covered with a soft 
synthetic resin such as silicone rubber. Rod-shaped halogen lamps of a 
normal rated power of 1360 W are provided inside the heat pressure rollers 
20 as heater lamps 21. The surface temperature of the heat pressure 
rollers 20 heated by the heater lamps 21 is controlled at a preferable 
temperature range, for example about 170.degree. C., which is lower than 
the bearable temperature of the silicone rubber. The heat pressure rollers 
20 are covered with a lower roller cover 16 and an upper roller cover 17 
so that an adverse effect of the heat from the heat pressure rollers 20 on 
the other electric control parts arranged in the casing 10 can be 
prevented. A baffle plate 17B is provided from a side wall 17A of the 
upper roller cover 17 on the guiding means 61 side toward the upper 
guiding plate 61B with small gap between the baffle plate 17A and the 
upper guiding plate 61B so as to limit the air passage through the small 
gap. That is, the baffle plate 17B serves as a limiting member for 
limiting the air flow in the space formed by the lower roller cover 16 and 
the upper roller cover 17. A side wall 16A of the lower roller cover 16 on 
the guiding means 61 side is bent to the direction away from the lower 
guiding plate 61A so that a large gap is provided between the side wall 
16A and the lower guiding plate 61A. That is, the bend of the side wall 
16A serves as a promoting portion for promoting the air outflow from the 
space formed by the lower roller cover 16 and the upper roller cover 17. 
Accordingly, the air outflow from the space formed by the lower roller 
cover 16 and the upper roller cover 17 is facilitated. As heretofore 
mentioned, the limiting member and the promoting portion comprise a 
guiding portion of the air in the space to the outside. 
The upper guiding plate 60B forming the inlet opening 12 will be explained 
in detail with reference to FIGS. 2 and 3. The upper guiding plate 60B has 
a substantially rectangular shape when viewed two-dimensionally, and the 
inlet opening 12 and the portion in the vicinity provide an upwardly bent 
inclined portion 60C. Two protruding portions 19A protruding downward and 
serving as air passage maintaining means are formed on the upper guiding 
plate 60B. The protruding portions 19A have a substantially-inverse 
trapezoid cross-sectional shape with the protruding height of about 1.0 mm 
to 1.68 mm, preferably 1.5 mm. The cross-sectional shape of the protruding 
portions 19 is not limited to the substantially-trapezoid shape, but can 
be a curved shape. Any shape can be applied as long as air passage can be 
provided for passing sufficient cooling air for cooling the heat pressure 
rollers 20 between the sheet assembly 108 and the upper surface or edge of 
the inlet opening portion 12 when the sheet assembly 108 is deformed and 
contacted with the protruding portion 19. The number of the protruding 
portion 19 is not limited to two as mentioned above. 
An exhaust fan 50 is provided at the bottom portion of the casing 10. By 
operating the exhaust fan 50, cooling air (outside air) is taken in from 
the inlet opening portion 12 so as to enter the space covered with the 
lower roller cover 16 and the upper roller cover 17 for cooling the heat 
pressure rollers 20. After cooling the heat pressure rollers 20, the 
cooling air is discharged by the exhaust fan 50 from the discharging 
opening formed at the bottom of the casing 10. A fin guard 51 is provided 
at the lower surface of the exhaust fan 50. 
As shown in FIG. 2, a control device 55 comprising electric control parts 
is provided below the conveyance path of the sheet assembly 108 in the 
casing 10. A plurality of slits 10B (see FIG. 5) are provided on the side 
wall 10A of the casing 10 in the vicinity of the control device 55 at a 
downward position with respect to the conveyance path so that the outside 
air for cooling is supplied to the control device 55 via the slits 10B for 
cooling the control device 55. A slit is not formed on the side wall 10A 
of the casing 10 in a position above with respect to the conveyance path 
so that the upper portion provide an inflow preventing portion 10C for 
preventing the inflow of the outside air into the casing 10. 
The operation of a heat device for a sheet 90 of an embodiment with the 
above-mentioned configuration of the present invention will be explained. 
A transfer sheet 100 on which an image has been formed based on digital 
data and a receptor sheet for printing 102 are superimposed on the 
auxiliary plate 104 comprising an aluminum plate of a 0.3 mm thickness so 
as to form a sheet assembly 108. When the sheet assembly 108 is inserted 
from the inlet opening portion 12 formed on the casing 10 along the inlet 
stand 11, the sheet assembly 108 is guided by the guiding means 60 so that 
the leading edge of the sheet assembly 108 is inserted between the pair of 
heat pressure rollers 20. Since the sheet assembly 108 is pressed in a 
heated state by the pair of the heat pressure rollers 20 in a rotating 
state, it is conveyed while the image on the transfer sheet 100 is heat 
transferred onto the receptor sheet for printing 102. The sheet assembly 
108 is guided by the guiding means 61, further conveyed by the discharge 
rollers 30, passes through the guiding means 62, and is discharged from 
the outlet opening portion 14. 
When the sheet assembly 108 is inserted from the inlet opening 12 formed on 
the casing 10 along the inlet stand 11, as mentioned above, the sheet 
assembly 108 may be deformed. However deformation it may be, since the 
protruding portions 19 are formed on the upper guiding plate 60B of the 
inlet opening portion 12, the sheet assembly 108 contacts only with the 
protruding portions 19A and thus does not contact with flat portions 19B. 
Accordingly, an air path for passing sufficient cooling air (outside air) 
passage for cooling the heat pressure rollers 20 can be provided between 
the sheet assembly 108 and the upper surface of the inlet opening portion 
12, as well as since the gap between the side wall 16A and the lower 
guiding plate 61A is set to be large, the air can be introduced by the 
exhaust fan 50 to the space covered with the lower roller cover 16 and the 
upper roller cover 17 via the gap between the upper guiding plate 60B and 
the sheet assembly 108 for cooling the heat pressure rollers 20, and the 
heated air in the space covered with the lower roller cover 16 and the 
upper roller cover 17 is discharged via the large gap between the side 
wall 16A and the lower guiding plate 61A. Therefore, since the heat 
pressure rollers 20 can be controlled at a constant temperature without 
temperature rise during the conveyance of the sheet assembly 108, problems 
such as uneven transfer and generation of wrinkles in the receptor sheet 
for printing due to difficulty of peeling off the transfer sheet and the 
receptor sheet for printing do not occur, and thus a transfer image 
extremely exact to the actual printed matter can be obtained on the 
receptor sheet. 
A preferable temperature for the upper heat pressure roller 20 is 
160.degree. C. to 190.degree. C., and a preferable temperature for the 
lower heat pressure roller 20 is 150.degree. C. to 180.degree. C. 
EXAMPLE 
FIG. 4 shows data of temperature rise by continuous paper or assembly feed. 
In FIG. 4, the solid line shows the temperature change of the upper heat 
pressure roller 20 with the protruding portions 19 of a projecting height 
of 1.5 mm, and the broken line (chain line) shows the temperature change 
of the lower heat pressure roller 20 with the protruding portions 19 of a 
projecting height of 1.5 mm. The dot line shows the temperature change of 
the upper heat pressure roller 20 with the protruding portions 19 of a 
projecting height of 1.0 mm, and the dashed line shows the temperature 
change of the lower heat pressure roller 20 with the protruding portions 
19 of a projecting height of 1.0 mm. The distance shown in FIG. 2 was 100 
mm, the distance b was 140 mm, and the distance c was 100 mm. 
As can be understood from the results of this experiment, with the 
projecting height of the protruding portions 19 of 1.5 mm, particularly 
preferable results were obtained.