Stamp apparatus with ink dispersing device

A stamp apparatus includes a supporting case which supports a printing sheet, an ink supply port through which ink is fed to the second surface of the printing sheet, and a dispersing device provided between the printing sheet and the supporting case. The dispersing device disperses ink supplied from the ink supply port uniformly over the surface of the printing sheet.

BACKGROUND OF THE INVENTION 
The present invention relates to a stamp apparatus using a printing sheet. 
As disclosed by Japanese Laid-Open Patent Application No. 7-251558, there 
is known a stamp apparatus using a porous printing sheet in which ink can 
be impregnated. A pattern is formed on a surface of the printing sheet, 
including a print portion which allows the permeation of ink and a 
non-print portion which block the permeation of ink. That is, ink is 
permeated through the printing sheet according to the pattern. The 
printing sheet is provided to the bottom of a body of the stamp apparatus. 
In order to repeatedly use the stamp apparatus without feeding ink 
thereto, the stamp apparatus is provided with an ink pad in which the ink 
is impregnated, the ink pad being interposed between the body and the 
printing sheet. When a user grips the body and urges the printing 
apparatus onto the medium so that the printing sheet is urged onto the 
medium, ink impregnated in the ink pad is transmitted through the printing 
sheet and transferred onto the medium. 
However, such a stamp apparatus has a disadvantage such that the ink pad 
must be replaced (together with the printing sheet) when the ink 
impregnated therein has been used up. Such replacement increases the 
running cost of the stamp apparatus. 
Another proposed stamp apparatus has an ink supply port (instead of the ink 
pad) provided in the body, through which ink can be fed to the printing 
sheet. 
However, there is a tendency that the amount of ink fed to the location (on 
the printing sheet) far from the ink supply port is smaller than the 
amount of ink fed to the location close to the ink supply port. 
Accordingly, ink is not uniformly fed over an entire surface of the 
printing sheet, which causes a deviation of the ink density of the pattern 
printed on the medium. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to enhance a uniformity 
of the density of a printed pattern. 
According to one aspect of the present invention, there is provided a stamp 
apparatus including a printing sheet (which selectively allows the 
permeation of ink according to a predetermined pattern) made of a porous 
sheet having first and second surfaces, a supporting case which supports 
the printing sheet so that the first surface is faced outside, an ink 
supply port (through which ink is fed to the second surface of the 
printing sheet) connected to the supporting case, and a dispersing device 
provided between the printing sheet and the supporting case. The 
dispersing device disperses ink supplied from the ink supply port 
uniformly over the second surface of the printing sheet. 
With such an arrangement, since the ink supplied from the ink supply port 
can be dispersed by means of the dispersing device, a uniformity of 
density of a printed pattern is improved. Further, since the stamp 
apparatus does not use an ink-pad (which should be replaced every time the 
impregnated ink is used up), the running cost of the stamp apparatus is 
reduced. 
In a particular arrangement, the dispersing device includes a base plate 
faced with the second surface of the printing sheet, and a plurality of 
ink holes formed on the base plate, through which ink flows to the second 
surface of the printing sheet. Particularly, the ink holes have different 
diameters so that, as the distance from the ink supply port to an ink hole 
increases, the diameter of the ink hole increases. 
There is a tendency that the amount of ink fed to the location far from the 
ink supply port is smaller than the amount of ink fed to the location 
close to the ink supply port. However, due to the setting of the diameter 
of ink holes of the dispersing device, ink is uniformly fed to the surface 
of the printing sheet. 
Further, the dispersing device includes a plurality of struts provided on 
the plate in such a manner that spaces are created between adjacent 
struts. With this, ink smoothly flows (through the spaces) to the location 
far from the ink supply port, which further improves the uniformity of the 
density of a printed pattern. 
In a preferred embodiment, the stamp apparatus further includes an outer 
frame in which the supporting case is movable in a certain direction, and 
a grip provided to the outer frame with a spring member disposed 
therebetween. The grip is coupled with the supporting case and is movable 
with respect to the outer frame. The spring member urges the supporting 
case and the grip so that the printing sheet is retracted in the outer 
frame. 
When the stamp apparatus is used, a user holds the grip to place the stamp 
apparatus on the medium. In this condition, the printing sheet is 
retracted in the outer frame. Then, the user urges the grip downward. The 
supporting case (and the printing sheet) is moved downward together with 
the grip, so that the printing sheet is moved to the position where the 
printing sheet is pressed against the medium. When the user releases the 
grip, the printing sheet quickly departs from the medium by the force of 
the spring member. Accordingly, the printing sheet quickly contacts and 
departs from the recording medium. It further improves the quality of the 
printed pattern. 
In another particular arrangement, the dispersing device includes a 
plurality of ribs provided between the ink supply port and the printing 
sheet. The ribs are extended from the ink supply port toward the printing 
sheet. As constructed above, ink falls along the inner surface of the ink 
supply port onto the ribs, and further falls along the surfaces of the 
ribs to reach the second surface of the printing sheet. Thus, the ink is 
uniformly fed to the printing sheet. 
Preferably, the ribs are in contact with the second surface of the printing 
sheet. With this, the printing sheet is supported by the ribs against the 
pressure when the printing sheet is urged onto the medium. Thus, the 
printing sheet is not loosened. The ribs are inwardly extended from an 
inner surface of the supporting case. Further, the ribs are integrally 
formed with the outer frame. Thus, the number of parts are reduced, which 
lowers a manufacturing cost of the stamp apparatus. Further, because of 
the ribs, the deformation of the outer frame (when the stamp apparatus is 
urged to the medium) can be prevented. 
In particular, the supporting case is divided into a plurality of sections 
by at least one partition wall. Additionally, a plurality of ink supply 
ports are provided to supply ink to the plurality of sections, 
respectively. With such an arrangement, it is possible to use different 
colors of ink for respective ink supply ports, which enables a color print 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A printing sheet and a stamp apparatus according to a first embodiment of 
the present invention are described with reference to FIGS. 1 to 5. 
FIG. 1 is a perspective view of a printing sheet. The printing sheet 1 is 
made of a porous sheet having pores in which ink can be impregnated. One 
surface (a print surface 1a) of the printing sheet 1 includes a print 
portion 3 and a non-print portion 2. The pores of the non-print portion 2 
are sealed so as to block the permeation of ink, while the pores of the 
print portion 3 are not sealed so as to allow the permeation of ink. Thus, 
the printing sheet 1 selectively allows the permeation of ink according to 
a predetermined pattern ("E" in the example of FIG. 1). The printing sheet 
1 has a rectangular shape. 
FIG. 2 is a side sectional view of a stamp apparatus 10 of the first 
embodiment. The stamp apparatus 10 is arranged to hold the printing sheet 
1 at one end portion thereof. A pattern is printed on a medium 26 (such as 
a paper) placed on a table 25. In the description hereinafter, the terms 
"tops", "bottom", "upward" and "downward" are defined at a condition where 
the stamp apparatus 10 is placed so that the printing sheet 1 faces the 
medium 26 as shown in FIG. 2. 
The stamp apparatus 10 includes a supporting case 11 which supports the 
printing sheet 1. The supporting case 11 is a flat box-shaped case with a 
bottom surface opened, including a rectangular top plate 11b and side 
plates 11a extended downward from the periphery of the top plate 11b. The 
printing sheet 1 is fit into the supporting case 11 so that the print 
surface 1a faces downward. The four edges of the printing sheet 1 are 
surrounded by the side plates 11a of the supporting case 11. A dispersing 
device 12 (detailed below) is interposed between the printing sheet 1 and 
the top plate 11b of the supporting case 11. 
An outer frame 13 is provided to cover and to movably support the 
supporting case 11. The outer frame 13 is a box-shaped case with a bottom 
surface opened, including a top plate 13b and side plates 13a extended 
downward from the periphery of the top plate 13b. The side plates 11a of 
the supporting case 11 is vertically slidable with respect to the inner 
surfaces of the side plates 13a of the outer frame 13, so that the 
supporting case 11 is vertically movable with respect to the outer frame 
13. The outer frame 13 is further provided with a guide portion 19 formed 
on the top plate 13b, which is covered by a grip 14 (described below) from 
above. 
The grip 14 is provided above the outer frame 13 with a spring unit 15 
interposed therebetween. The grip 14 is cap-shaped and includes a top 
plate 14b and a skirt 14a extending downward from the periphery of the top 
plate 14b. When the grip 14 covers the guide portion 19 of the outer frame 
13, the internal surface of the skirt 14a contacts the guide portion 19. 
In order to couple the grip 14 and the supporting case 11, three coupling 
members 16 are integrally provided on the top plate 11b of the supporting 
case 11, which are protruded upward through holes 18 formed on the top 
plate 13b of the outer frame 13. The grip 14 is provided with three 
tubular supports 20 extending downward from the top plate 14b of the grip 
14 so that the coupling members 16 are fit into the tubular supports 20. 
Thus, the grip 14 is vertically slidable (together with the supporting 
case 11) with respect to the outer frame 13. 
One of three coupling members which is located at the center of the 
supporting case 11 includes a vertically extending passage. The passage 
serves as an ink supply port 17 through which ink can be supplied to the 
printing sheet 1. 
The spring unit 15 is provided between the bottom of the tubular support 20 
and the top plate 13b of the outer frame 13. The spring unit 15 includes a 
bent plate spring 21 and urges the outer frame 13 downward with respect to 
the supporting case 11 and the grip 14. When no force is applied to the 
grip 14, the bottom end of the outer frame 13 is positioned lower than the 
print surface 1a of the printing sheet 1 (due to the force of the spring 
unit 15) by an amount H1 as shown in FIG. 2. Thus, the printing sheet 1 is 
retracted in the outer frame. The interval between the bottom end of the 
skirt 14a and the top plate 13b of the outer frame 13 is set to H2 which 
is greater than H1. When a user pushes the grip 14 downward, the grip 14 
and the supporting case 11 are moved downward resisting the force of the 
spring unit 15, so that the printing sheet 1 can be pressed onto the 
medium 26. 
FIG. 3 is a sectional view of the stamp apparatus 10 taken along a line 
III--III of FIG. 2. FIGS. 4 and 5 are a plan view and a partially cutaway 
perspective view of the dispersing device 12. As shown in FIG. 3, the 
dispersing device 12 includes a base plate 22 which is faced with a back 
surface 1b (a surface opposite to the print surface 1a) of the printing 
sheet 1. Struts 23 are provided on the base plate 22 at a predetermined 
interval, which are protruded upward toward the top plate 11b of the 
supporting case 11. As shown in FIG. 5, spaces are created between 
adjacent struts 23 and between the top plate 11b and the base plate 22. 
The spaces are connected with each other. 
As shown in FIG. 4, the base plate 22 is provided with ink holes 24a, 24b, 
24c and 24d which penetrate the base plate 22 and open in the spaces 
between respective struts 23. The ink supplied onto the upper surface of 
the base plate 22 is transmitted to the back surface 1b of the printing 
sheet 1 through the ink holes 24a, 24b, 24c and 24d. Further, the ink 
holes 24a, 24b, 24c and 24d have different diameters so that, as the 
distance from the ink supply port 17 increases, the diameter of the ink 
hole increases. In particular, the ink hole 24a is located at the closest 
position to the ink supply port 17, with ink hole 24b, 24c and 24d 
following in that order. The ink hole 24d has the largest diameter, with 
the ink hole 24c, 24b and 24a following in that order. There is a tendency 
that the amount of ink fed to the location far from the ink supply port 17 
is smaller than the amount of ink fed to the location close to the ink 
supply port 17. However, due to the setting of the diameter of the ink 
holes 24a, 24b, 24c and 24d, ink is uniformly fed to the back surface 1b 
of the printing sheet. 
As constructed above, ink supplied from the ink supply port 17 is uniformly 
fed to the back surface 1b of the printing sheet 1 (through the ink holes 
24a, 24b, 24c and 24d) and is uniformly impregnated in the printing sheet 
1. 
When the stamp apparatus 10 is used, a user holds the grip 14 to place the 
stamp apparatus 10 on the medium 26 and pushes the grip 14 downward. The 
movement of the grip 14 moves the supporting case 11 (and the printing 
sheet 1) downward resisting the force of the spring unit 15, so that the 
printing sheet 1 is pressed against the surface of the medium 26. When the 
user releases the grip 14, the printing sheet 1 quickly departs from the 
medium 26. Accordingly, the printing sheet 1 quickly contacts and departs 
from the medium 26. 
Since ink is uniformly impregnated in the printing sheet 1, ink is 
uniformly transmitted on the medium 26. Accordingly, the density of the 
pattern formed on the medium 26 becomes uniform. Particularly, the blur of 
the periphery of the pattern can be prevented. Further, because of the 
spaces between the struts 23, ink supplied from the ink supply port 17 is 
smoothly fed to the location far from the ink supply port 17. Thus, the 
uniformity of the density of the pattern is further improved. 
In the first embodiment, the above described components of the stamp 
apparatus 10 can be made of a synthetic resin. Further, it is possible to 
divide the space (on the base plate 22) into several sections and to 
provide several ink supply ports for respective sections. It enables color 
print, by using inks of several colors in respective sections. It is 
further possible to replace the spring unit 15 with a coil spring provided 
around the coupling member 16. Further, it is possible to provide through 
holes penetrating the top plate 11b of the supporting case 11 and to use 
the through holes instead of the ink supply port 17. Further, the stamp 
apparatus can be constructed by providing a grip 14 to the upper surface 
of the top plate 11b of the supporting case 11, without the outer frame 13 
and the spring unit 15. Additionally, a detachable cover (not shown) can 
be provided to the lower end of the outer frame 13 or the supporting case 
11 to cover the print surface 1a of the printing sheet 1. 
The second embodiment of the present invention is described. 
FIG. 6 is a sectional view of the stamp apparatus 110 of the second 
embodiment. The stamp apparatus 110 uses the printing sheet 1 having a 
circular shape. The features of the printing sheet 1 except its shape are 
the same as the printing sheet 1 described in the first embodiment. 
The stamp apparatus 110 includes a cylindrical supporting case 111 with a 
bottom surface opened, including a circular top plate 111b and a skirt 
portion 111a extending downward from the circumference of the top plate 
111b. The printing sheet 1 is fit into the bottom of the supporting case 
111 so that the gap between the periphery of the printing sheet 1 and the 
skirt portion 111a is sealed. Dispersing ribs 112 (detailed later) are 
formed in the supporting case 111. An outer frame 113 is provided to 
support the supporting case 111 from outside. The outer frame 113 has a 
tubular shape, including upper and lower cylinder portions 113b and 113a 
respectively. The supporting case 111 is vertically slidable in contact 
with the inner surface of the lower cylinder portion 113a. 
An ink supply port 116 is provided to the supporting case 111. The ink 
supply port 116 is a cylindrical member integrally formed in line with the 
supporting case 111, and surrounded by the upper cylinder portion 113b. 
The ink supply port 116 is provided with a passage 116a which opens at 
both ends. The upper end of the passage 116a is closed by a lid 117. When 
the lid 117 is removed, ink can be supplied to the supporting case 111 
through the passage 116a. 
A grip 114 is provided above the outer frame 113. The grip 114 is 
cap-shaped and includes a top plate 114b and a skirt 114a extending 
downward from the periphery of the top plate 114b. The skirt 114a is in 
contact with the upper cylinder portion 113b. In order to prevent the 
rotation of the grip 114 with respect to the outer frame 113, the outer 
frame 113 is provided with a bar 118 which engages a vertically extending 
groove 119 provided to the inner surface of the grip 114. In order to 
detachably mount the grip 114 to the supporting case 111, the grip 114 is 
provided with a tubular support 120 extending downward from the top plate 
114b. The tube 120 is provided with projections 120a inwardly projecting 
from the inner surface thereof. Each projection 120a elastically engages 
with a recess 121 formed at the outer surface of the ink supply port 116. 
A coil spring 122 is interposed between the outer surface of the ink supply 
port 116 and an inner surface of the upper cylinder portion 113b of the 
outer frame 113. The upper end of the coil spring 122 abuts an upper 
stopper 123 provided around the ink supply port 116. The lower end of the 
coil spring 122 abuts a lower stopper 113c provided to the outer frame 
113. That is, the coil spring 122 urges the outer frame 113 downward with 
respect to the ink supply port 116 and the supporting case 111. Thus, when 
no force is applied to the grip 114, the supporting case 111 are lifted up 
with respect to the outer frame 113 so that a bottom end of the lower 
cylinder portion 113a of the outer frame 113 is lower than the print 
surface 1a of the printing sheet 1 (by a distance H1). Thus, the printing 
sheet 1 is retracted in the outer frame 113. The interval between the 
bottom end of the skirt portion 114a and the upper cylinder portion 113b 
of the outer frame 113 is set to H2 which is greater than H1. 
When a user pushes the grip 114 downward, the supporting case 111 and the 
ink supply port 116 are moved downward resisting the force of the coil 
spring 122, so that the printing sheet 1 can be pressed against the 
surface of the medium 26. When the user releases the grip 114, the 
printing sheet 1 quickly departs from the medium 26. Accordingly, the 
printing sheet 1 quickly contacts and departs the medium 26. 
FIGS. 8 and 9 are a bottom perspective view and a bottom view of the 
supporting case 111 and the dispersing ribs 112. The dispersing ribs 112 
are inwardly extended from an inner surface of the skirt portion 111a of 
the supporting case 111. Further, the dispersing ribs 112 are extended 
from the top plate 111b of the supporting case 111 toward the printing 
sheet 1. The lower ends of the dispersing ribs 112 are in contact with the 
back surface 1b of the printing sheet 1 (FIG. 6). As shown in FIG. 9, 
several dispersing ribs 112a are extended to a portion below the lower end 
of the passage 116a of the ink supply port 116. The periphery of the 
printing sheet 1 is adhered to the skirt portion 111a by means of adhesive 
or heat press. Particularly, the supporting case 111 is made of 
acrylonitrile-butadienestyrene (ABS) plastic and the printing sheet 1 is 
made of urethane plastic, so that the supporting case 111 and the printing 
sheet 1 can be well adhered by means of heat-press. A vertical gap between 
the print surface 1a of the printing sheet 1 and the bottom end of the 
skirt portion 111a of the supporting case 111 is set to approximately 0.5 
mm. With this, when the printing sheet 1 is urged to the medium 26, a 
heat-pressed portion of the printing sheet 1 does not suffer from a large 
amount of deformation, which improves the durability of the printing sheet 
1. Further, it is possible to adhere the bottom ends of several dispersing 
ribs 112 to the back surface of the printing sheet 1 by means of an 
adhesive, so that printing sheet 1 are not peeled off from the dispersing 
ribs 112. 
On supplying ink to the stamp apparatus 110, the grip 114 is detached from 
the supporting case 111 and the lid 117 is removed from the ink supply 
port 116. Then, ink is poured from the upper end of the passage 116a of 
the ink supply port 16. Ink falls along the inner surface of the passage 
116a onto the dispersing ribs 112, and further falls along the surfaces of 
the dispersing ribs 112. Finally, ink reaches to the back surface 1b of 
the printing sheet 1 and is impregnated in the printing sheet 1. 
As constructed above, the ink is uniformly fed over entire surface of the 
printing sheet 1. Further, since the dispersing ribs 112 exist behind the 
printing sheet 1, the printing sheet 1 is not loosened. Further, because 
of the dispersing ribs 112, the deformation of the outer frame 113 (when 
the stamp apparatus 110 is pressed to the medium 26) can be prevented. It 
is preferable that a detachable cover 128 (FIG. 7) is provided to the 
lower end of the outer frame 113 or the supporting case 111 to cover the 
printing surface 1a of the printing sheet 1. 
FIG. 10 shows a modification of the supporting case of the second 
embodiment. In a supporting case 211 of the modification, a trapezoid wall 
211b is provided between the skirt portion 111a and the ink supply port 
116, instead of top plate 111b. Accordingly, ink (which has fallen along 
the inner wall of the passage 116a) easily falls downward along the 
trapezoid wall 211b. Thus, the ink is quickly and uniformly fed to the 
printing sheet 1. 
The third embodiment of the present invention is described. 
FIGS. 11, 12 and 13 are a side view, a bottom view and a perspective view 
of a stamp apparatus 310 of the third embodiment. Although a grip is 
omitted in FIGS. 11, 12 and 13, the grip is constructed in a substantially 
similar manner to the grip 114 of the second embodiment. The stamp 
apparatus 310 includes a square shaped supporting case 311, including a 
top plate 311b and side plates 311a extending downward from the periphery 
of the top plate 311b. A cavity defined by the top plate 311b and side 
plates 311a is divided into three sections by two partition walls 329. 
Three ink supply ports 316 are respectively provided to the three sections 
of the supporting case 311. Each ink supply port 316 is constructed in a 
similar manner to the ink supply port 116 of the second embodiment and has 
a passage 316a with both ends opened. The top end of the passage 316a is 
closed by a lid (not shown) which is similar to the lid 117 (FIG. 6) of 
the second embodiment. 
As shown in FIGS. 12 and 13, dispersing ribs 312 are respectively provided 
in the three sections of the supporting case 311. In each section, 
dispersing ribs 312 extend from the side plates 311a and the partition 329 
toward the center of the section. The bottom ends of the dispersing ribs 
312 are in contact with the top surface of the printing sheet 1 (FIG. 11). 
As shown in FIG. 12, several dispersing ribs 312a are extended to a 
portion below the lower end of the passage 316a of the ink supply port 
316. As shown in FIG. 11, three printing sheets 1 are provided to the 
respective sections of the supporting case 311. 
As constructed above, the ink is quickly and uniformly fed to the printing 
sheet 1. Further, since the ink of respective sections do not mix with 
each other, it is possible to use different colors of ink for respective 
ink supply ports 316, which enables a color print. 
FIG. 14 is a side view of a modification of the stamp apparatus of the 
third embodiment. In the stamp apparatus 410, the supporting case 411 is 
divided into three sections by two partition walls 429. However, one 
printing sheet 1 is provided to the supporting case 411 so that the 
printing sheet 1 covers the lower ends of all sections thereof. The 
printing sheet 1 is adhered to the side plates 311a by means of an 
adhesive or heat-press. It is preferred that the bottom end of each 
partition 429 is in contact with and adhered to the upper surface of the 
printing sheet 1. With such an arrangement, if ink of one color is 
supplied to the ink supply ports 316, a large pattern can be obtained. 
Further, if different colors of ink are used for respective ink supply 
ports 316, color image can be obtained. 
In the second and third embodiments, it is possible that the supporting 
case 111 (or 311) is made of synthetic resin and manufactured by injection 
molding. With this, it becomes easy to integrally manufacture the 
supporting case 111 (or 311) and the dispersing ribs 112. Furthermore, the 
stamp apparatus can be constructed by providing the grip 114 to the upper 
surface of the top plate 111b of the supporting case 111 (or 311), without 
the outer frame 113 and the spring unit 15. It is further possible to 
provide through holes penetrating the top plate 111b of the supporting 
case 111 and to use the through holes instead of the ink supply port 116. 
Finally, a manufacturing process of the printing sheet 1 is briefly 
described. The printing sheet 1 is manufactured by a not shown 
manufacturing device provided with a flash bulb capable of irradiating 
infrared rays. A porous sheet (in which ink can be impregnated) is used as 
a base material of the printing sheet. A black film having a surface 
coated with carbon is used to heat the surface of the porous sheet. An 
original sheet is made of a material which allows the permeation of 
infrared rays, while a pattern (such as a character, figure, or the like) 
is formed by a material which blocks infrared rays. 
The porous sheet, the black film and the original sheet are overlapped and 
laid on a transparent plate. The overlapped sheets are pressed so that the 
porous sheet contacts the black film and the black film contacts the 
original sheet. Then, the flash bulb irradiates infrared rays to the 
original sheet through the transparent plate. Infrared rays irradiated 
onto the pattern on the original sheet are blocked, whereas infrared rays 
irradiated onto non-pattern portion pass through the original sheet. The 
infrared rays passing through the original sheet reach the black film 
causing the black film to generate heat. The heated surface of the porous 
sheet is caused to melt such that pores near the surface thereof are 
sealed. Conversely, since the infrared rays are blocked by the pattern of 
the original sheet, the portion of the black film which corresponds to the 
pattern does not generate heat, so that the pores near the surface of the 
porous sheet corresponding thereto are not sealed. 
Thus, a print portion 3 in which pores are opened and a non-print portion 2 
in which pores are sealed are formed on the surface of the porous sheet as 
shown in FIG. 1. With such a process, the printing sheet 1 is formed. 
It is alternatively possible to disperse carbon grains or other material 
(for example, silver chloride or silver bromide) which absorbs infrared 
rays. The porous sheet can be made of a foamed resin made of polyolefin 
resin, polyvinyl chloride resin, polyurethane resin or other material 
which shows flexibility and softness when formed into the porous sheet. 
Pores are disposed over a surface of the porous sheet (before the pattern 
is formed on the surface of the porous sheet). Particularly, the thickness 
of the porous sheet is 1 to 5 mm. When such porous sheet is overlapped 
with the original sheet and exposed to the infrared rays irradiated 
through the original sheet, the porous sheet absorbs infrared rays and 
generates heat itself. Thus, it is not necessary to provide a black film. 
It is preferred that the content of the carbon in the porous resin sheet 
38 is in the range of 0.01-15 wt %. With this, the porous resin sheet is 
gray and, when heated, turns black. Accordingly, it can be confirmed which 
of various colors of ink has been impregnated in the porous resin sheet. 
Further, since the carbon is greater than or equal to 0.01 wt %, the 
porous resin sheet is easily heated (such that the pores at the surface 
thereof are sealed) by a standard flash bulb. 
The original sheet is made of a material (such as a copy paper) which 
allows the permeation of light, on which a pattern is formed using ink or 
paint which blocks the transmission of light. The porous sheet is 
overlapped with the original sheet with a transparent film sandwiched 
therebetween. The transparent film is made of a material having a high 
melting point and the thickness thereof is 0.025 to 0.2 mm. The porous 
sheet, the transparent film and the original sheet are overlapped and laid 
on the transparent plate so that the pattern on the surface of the 
original sheet contacts the transparent film. Then, the flash bulb 
irradiates infrared rays to the original sheet through the transparent 
plate. Infrared rays irradiated onto the pattern on the original sheet are 
blocked, whereas infrared rays irradiated onto non-pattern portion pass 
through the original sheet. The infrared rays passing through the original 
sheet reach the porous sheet, causing the carbon black to generate heat. 
The heated portion melts such that pores thereof are sealed. Conversely, 
since the infrared rays are blocked by the pattern of the original sheet, 
the portion of the porous sheet which corresponds to the pattern does not 
generate heat, so that the pores of the porous sheet corresponding thereto 
are not sealed. Thus, the print sheet 1 is formed. In the above described 
process, the pattern on the original sheet tends to be heated by the 
irradiation of the infrared rays. However, since the heat of the pattern 
of the original sheet is dispersed in the transparent film, the heat of 
the pattern of the original sheet does not affect the porous sheet to 
melt. 
Although the structure of a stamp apparatus is described herein with 
respect to the preferred embodiments, many modifications and changes can 
be made without departing from the spirit and scope of the invention. 
The present disclosure relates to subject matter contained in Japanese 
Patent Application Nos. HEI 8-309022, filed on Nov. 20, 1996 and HEI 
09-64596, filed on Mar. 18, 1997, which are expressly incorporated herein 
by reference in its entirety.