Medium processing apparatus and ejected medium drop prevention mechanism

After the medium has been processed by the medium processing apparatus 100 (receipt journal printer), it lands on the top cover 120 of the medium processing apparatus 100 as a curled medium 160. The ejected medium drop prevention mechanism 110 is disposed at the point where the edge of the ejected medium lands. The ejected medium drop prevention mechanism 110 has a ladder like structure and holds the edge of the ejected medium by introducing the edge into the opening of the ladder like structure, thereby preventing the ejected medium from dropping down.

TECHNICAL FIELD 
This invention relates to a system for holding a medium ejected from a 
medium processing apparatus and, particularly, to an improved ejected 
medium drop prevention mechanism. 
BACKGROUND 
A receipt journal printer of a Point-of-Sale (POS) prints on rolled paper 
and cuts the printed paper (a medium such as paper ejected from a medium 
processing apparatus such as a printer is hereinafter called "ejected 
medium" regardless of whether it is printed or not) using a cutter. 
When the ejected medium, outputted from a printer, is short in length, it 
stays on a top cover of the printer without dropping down to the back of 
the printer. However, when the ejected medium is very long as shown in 
FIG. 11, it drops down to the back of the printer. 
An account statement printed in a receipt journal printer of POS at the end 
of daily business is often as long as 50 cm and drops down to the back of 
the printer when the ejected medium is cut upon completion of printing. 
Because the account statement printed at the end of daily business takes a 
long time to print, it was desired that it was printed without operator 
attendance, but it had to be watched by an operator to prevent the medium 
from dropping down to the back of the housing of the printer. 
Relating to such a problem of the eject mechanism of a printer, 
PU-226776 discloses, in its first embodiment, a provision of a forward 
eject guide in the medium eject exit so as to have the ejected medium drop 
in the front of the printer housing to prevent it from dropping to the 
back of the printer. Also, the second embodiment of the same PUPA 
discloses a provision of a medium take-up guide in the medium eject exit 
so as to take up the medium to prevent it from dropping to the back of the 
printer. 
However, because such guide is of a structure protruding from the housing 
of a printer, use entails the following drawbacks: 
1. It hinders exchanges with customers when giving change or receiving 
money. 
2. It can be easily damaged. 
3. An item cannot be put on the printer (especially when the printer is in 
operation). 
4. The ejected medium curls toward the printed surface to make the printed 
content invisible or unreadable. 
5. The appearance design of printer is largely restricted. 
6. The ejected medium drops to the front and may be stained in the forward 
eject guide. It is not easy to take out the ejected medium in the medium 
take up guide. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a medium processing apparatus 
in which an ejected medium does not drop even when a long medium is 
ejected. 
It is another object of this invention to provide an ejected medium drop 
prevention mechanism while maintaining a characteristic of user friendly 
medium processing apparatus without hindering working the exchange of 
items with the customer. 
It is another object of this invention to provide an ejected medium drop 
prevention mechanism which has a low probability of being damaged. 
It is a further object of this invention to provide an ejected medium drop 
prevention mechanism which does not hinder observation of the printed 
surface of the ejected medium. 
It is a further object of this invention to provide an ejected medium drop 
prevention mechanism which is less restrictive in designing the appearance 
of the printer. 
It is a further object of this invention to provide a user friendly ejected 
medium drop prevention mechanism which allows the ejected medium to be 
simply taken up without requiring any special operation. 
In accordance with an embodiment of the present invention, an ejected 
medium drop prevention mechanism is disposed at a point where the medium 
touches a top cover, etc., of a medium processing apparatus with the 
medium curled after it is processed by the medium processing apparatus. 
The ejected medium drop prevention mechanism is provided with an opening 
leading to an internal space in the side of eject exit for allowing the 
edge of the ejected medium to enter the opening. The opening holds the 
edge of the ejected medium to prevent the ejected medium from dropping 
down. 
In another embodiment of this invention, a medium processing apparatus is 
provided which ejects a curled medium after processing and cuts off said 
ejected medium after the process ends. The apparatus has a cutter for 
cutting off said ejected medium, a top cover, and an ejected medium drop 
prevention mechanism disposed at a position where the edge of said ejected 
medium lands on said top cover and provided with a plurality of bars 
forming a ladder like shape which is disposed so as to provide a space 
between the bars and said top cover. 
In another embodiment of this invention, a medium processing apparatus is 
provided which ejects a curled medium after processing and cuts off said 
ejected medium after the process ends. The apparatus has a cutter for 
cutting off said ejected medium, a top cover, and an ejected medium drop 
prevention mechanism disposed at a position where the edge of said ejected 
medium lands on said top cover and provided with an opening having a space 
into which the edge of the ejected medium move along the direction of the 
curl. 
In another embodiment of this invention, a medium processing apparatus is 
provided which can process a medium of different lengths and ejects a 
curled medium after processing. The apparatus has an ejected medium drop 
prevention mechanism disposed at a position where the edge of said ejected 
medium lands and provided with an opening having a space into which the 
edge of the ejected medium moves along the direction of the curl. 
In another embodiment of this invention, provided is an ejected medium drop 
prevention mechanism disposed at a position where the edge of said ejected 
medium lands on said top cover of a medium processing apparatus which 
ejects a curled medium after processing and cuts off said ejected medium 
after the process ends, said mechanism is provided with a plurality of 
bars forming a ladder like shape which is disposed so as to provide a 
space between the bars and said top cover. 
In another embodiment of this invention, provided is an ejected medium drop 
prevention mechanism disposed at a position where the edge of said ejected 
medium lands on a medium processing apparatus which can process a medium 
of different lengths and ejects a curled medium after processing, said 
mechanism is provided with a plurality of openings having a space into 
which the edge of the ejected medium move along the direction of the curl.

DETAILED DESCRIPTION 
The term "medium processing apparatus" is defined as a concept embracing 
various printers including a receipt journal printer. The term "ejected 
medium" is described as an object to be operated upon or work piece, and 
is not an element of this invention. 
FIG. 1 shows the appearance of an embodiment of a printer 100 of this 
invention. FIG. 2 is a cross sectional view of an ejected medium drop 
prevention mechanism 110 provided in the printer 100. 
The ejected medium drop prevention mechanism 110 in a preferred embodiment 
of this invention has a ladder like structure and is disposed at a point 
where a receipt is landed. In this example, the ejected medium drop 
prevention mechanism 110 is formed by modifying the top cover 120 of IBM 
4689-301 Receipt Journal Printer and, specifically, is integrally formed 
by molding a resin. While the ejected medium drop prevention mechanism 110 
is formed by molding a resin in the preferred embodiment of this 
invention, it may be formed of a sheet metal as well. 
In the example shown in FIG. 1 and FIG. 2, bars 131 through 137 are of a 
square cross section of 8 mm by 8 mm and are disposed in a position 7 mm 
above the cover surface of the printer. The pitch 151 of the bars is 
designed to be 20 mm (the length of the openings 171 through 177 is 
therefore designed to be 12 mm). 
If the length of the opening is too long, sufficient frictional force is 
not obtained to hold an ejected medium. On the other hand, if the length 
is to short, the end of the ejected medium may not enter the opening due 
to twist of the ejected medium, etc., and the medium may be curled on the 
bar. Accordingly, it is desirable to set the length of the opening to 
about 13 to 28 mm when this invention is applied to the roll paper for a 
POS printer. Also, the width of the opening is designed to be sufficiently 
wider than the ejected medium taking a lateral shift of the ejected medium 
into consideration. 
Similarly, if the space between the bars 131 through 137 and the cover 
surface is too wide, a sufficient frictional force is not obtained to hold 
the ejected medium. On the other hand, if the space is too narrow, the end 
of the medium may be caught by the bar due to curling and twisting of the 
ejected medium inhibiting the end of the medium from moving into the space 
beneath the bars. Therefore, it is desirable to set the space between the 
bars and the cover surface to about 3 to 15 mm when this invention is 
applied to the roll paper for a POS printer. 
On the other hand, a ladder like structure is adopted in the ejected medium 
drop prevention because the paper tends to curl differently depending on 
the diameter of the rolled paper (large at the beginning of use and small 
at the end of use) resulting in different landing points of the ejected 
paper. 
FIG. 3 shows the case of a minimum curl while FIG. 4 shows the case of a 
maximum curl. In a typical roll paper for a POS printer, outer diameter of 
the roll is 80 mm at the beginning of use while it is 20 mm at the end of 
the roll. 
According to the result of an experiment using IBM 4689-301 Receipt Journal 
Printer, the radius of curl was 41 mm and the distance of landing from the 
exit was 109 mm at the beginning of use. When the roll paper is almost 
ending, the radius of curl was 20 mm and the distance of landing from the 
exit was 46 mm. Accordingly, the opening 171 which is furthest from the 
eject exit is disposed at a position somehow further from the maximum 
landing point while the opening 177 which is nearest the eject exit is 
disposed at a position somehow nearer the minimum landing point. 
Because the optimum values of the shape and the position of the ejected 
medium drop prevention mechanism vary depending on the structure of a 
platen (radius, etc.), feed speed, printing impact pressure, properties of 
the ejected medium (material, thickness, width, etc.), temperature, 
humidity, angle of ejection, angle between the eject exit and the cover, 
and positional relationship there between, it is desirable to take these 
factors into consideration. 
The process in which the ejected medium drop prevention mechanism holds the 
ejected medium is next explained in the sequence of operations with 
reference to FIG. 3 to FIG. 5. As shown in FIG. 3, when the ejected medium 
160 is progressively fed out from the eject exit 185 of the medium 
processing apparatus 100, the leading edge of the ejected medium 160 drops 
into either one of the openings 171 through 177 which are formed by the 
bars 131 through 137 (even if the leading edge of the ejected medium lands 
on a bar, the edge drops without fail into the space between the bars by a 
progressive feeding of the ejected medium because the openings 171 through 
177 of the ejected medium drop prevention mechanism 110 are designed 
taking twist or lateral shift of the edge of the ejected medium into 
consideration). 
Thereafter, as the ejected paper is fed out, the outer surface of the 
curled paper (the printing surface in this example) touches the bar 135 
which is positioned after the opening (opening 177 in the example of FIG. 
3) into which the edge of the ejected medium 160 drops and the edge is 
prevented from moving toward the rear of the printer. As the ejected paper 
is further fed out, the leading edge moves toward the front of the printer 
conversely until the inner surface of the curled paper (back of the 
printing surface in this case) contacts to the bar 133 (the edge of the 
ejected paper moves into the space beneath the bar 137 which lies inside 
the curl). 
When the ejected paper is further fed out after the inner surface of the 
curled paper touches the bar 133, a moment and a stress are generated 
around the corner 132 of the bar 131 by virtue of the resilience of the 
ejected paper (generated by stretching the curl) and the weight of the 
paper. The stress is also generated at the corner 134. As a result, a 
sufficient frictional force is generated at the corners 132 and 134 to 
prevent the ejected paper from dropping. 
As such, the receipt is held without dropping down as shown in FIG. 5 and 
FIG. 6 even if the ejected medium is cut after the folding part 136 of the 
ejected medium has moved to the rear of the cover 120 of the printer. 
Thus, the operator can simply take the receipt by taking it up as it is. 
FIG. 6 to FIG. 9 show alternative embodiments of this invention. FIG. 6 and 
FIG. 7 show an example in which the shape of the bars 131 through 137 are 
so modified as to make the edge of the ejected medium 160 more easily 
enter the openings 171 through 177. While the bars 131 through 137 have a 
triangular cross section, they may have other cross section such as a 
parabolic or a circular cross section. 
Incidentally, in the example of FIG. 7, the ejected medium 160 once having 
entered the openings 171-177 may slide up the triangular slope of the bars 
131-137 so that the embodiment of FIG. 6 is preferable. 
FIG. 8 shows an example in which the ejected medium drop prevention 
mechanism 110 is embedded in the top cover 120. With this embodiment the 
top surface of the medium processing apparatus 100 is open for other use 
because the ejected medium drop prevention mechanism 110 does not protrude 
from the top cover 120. The ladder frame including the bars may be made 
detachable so that dust inside the ejected medium drop prevention 
mechanism 110 may be easily cleaned off. 
FIG. 9 shows an example which is designed taking different radii of the 
curl at different landing positions into consideration. While the edge of 
the ejected paper 160 arriving at the proximity of the eject exit 185 can 
move into the space beneath the bar 137 even though the space between the 
bar 137 and the top cover 120 is narrow because the radius of the curl is 
small, the edge of the ejected paper 160 arriving at a position further 
from the eject exit 185 can not move into the space beneath the bar 137 if 
the space between the bar 137 and the top cover 120 is narrow because the 
radius of the curl is large. 
On the other hand, when the radius of the curl is small, a narrower spacing 
between the bar and the top cover 120 gives a higher holding force to the 
ejected medium 160 than the case where the radius of the curl is large. As 
such, it is so designed that the space between the bar and the top cover 
120 is narrow near the eject exit 185 while it is wider in positions 
further from the eject exit 185. 
FIG. 10 shows an example in which the ejected medium drop prevention 
mechanism 110 is detachable from the top cover 120. In the example shown, 
a magnet is embedded in the bottom 138 of the ejected medium drop 
prevention mechanism 110 so that it is attached to the top cover 120 (a 
magnetically attractive material such as a steel sheet is used on the 
surface of or inside the top cover 120 in this example). Conversely, the 
top cover 120 may include a magnet. 
In the preferred embodiment of this invention, a position where the ejected 
medium drop prevention mechanism 110 is to be set is marked on the top 
cover 120. However, in order to prevent the edge of the ejected paper 160 
landing furthest from the eject exit 185 from passing over the wall 130 of 
the ejected medium drop prevention mechanism 110 even when a user sets the 
mechanism 110 somehow out of the right position, the wall 130 is so 
designed that it is taller than the bars 131-137 as shown in FIG. 10. 
While the ejected medium drop prevention mechanism 110 is made detachable 
from the top cover 120 by means of a magnet in this example, other means 
may be used to make it detachable, including a sucking disk, velcro, a 
screw as well as a slide mechanism (a groove is provided in one of the 
mechanism 110 and the top cover 120 and the other is provided with a 
protrusion engaging with the groove) and a latch mechanism or a 
combination thereof. 
As described in the above, this invention provides a user friendly ejected 
medium drop prevention mechanism which has an advantage in that: 
1. it does not hinder working; 
2. it has a low probability of being damaged; 
3. it does not hinder observation of the printed surface of the ejected 
medium; 
4. appearance design is less restricted; 
5. the ejected medium can be simply taken up without requiring a special 
operation. 
While the invention has been described in terms of preferred embodiments, 
those skilled in the art will recognize that the invention can be 
practiced with modification within the spirit and scope of the appended 
claims.