Printing apparatus

In an impact type printing apparatus, leak of impact noise to outside can be reduced by (1) arranging the print head, platen and sheet exhaust port almost in a line and (2) setting the shape of guide ribs provided at the internal surface of cover having the aperture so that the envelope of guide ribs which has come closest to the platen at the center and periphery thereof of the sheet and is gradually separated from the platen at both ends of the sheet. Moreover, the optimum exhaust port can be selected depending on the type and thickness of sheet by rotation of cover or providing the slide mechanism.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to an improvement of a printing apparatus 
which conducts printing by giving impact to a printing medium set on the 
platen with a print head and then ejects the printing medium from an 
exhaust port. 
An impact printer such as a wire dot-matrix printer is already used widely 
because of its low-cost characteristics and duplicating function. 
However, such impact printer generates impact noise during the printing 
operation and such impact noise is considered as a problem of this 
printer. Recently, the printing apparatus has often been installed in 
offices as an output device of a personal computer, etc. and therefore it 
has also been intensively requested to reduce the level of printing noise. 
Particularly, the front end noise of the printer results in a serious 
problem because an operator usually stays in front of the printer. 
It has of course been discussed how to suppress the impact noise generated 
during printing operation by improvement of the print head itself, but the 
method to suppress impact noise is naturally has a limitation. Therefore, 
it is also necessary, from the structural view point of apparatus, to 
realize reduction of impact noise. 
Meanwhile, it is also impressively expected that a printing apparatus 
accepts a variety of printing media, such as papers in different thickness 
and rigidity, for example, an ordinary paper and paper-stapled sheet [a 
plurality of papers are gathered and bound with a pressing force thereto]. 
(2) Description of the Prior Art 
FIGS. 1(a), 1(b) respectively show conventional printers. In the printer 
shown in FIG. 1(a), an aperture 3a designed as the exhaust port for papers 
is provided above the platen 2 and a print head is also provided at the 
left side of platen 2. 
The print head 1 makes spacing movement along the platen 2 to execute the 
printing on a cut sheet inserted from the guide 6 or a continuous sheet 
transferred by a tractor 5. A bail roller 4 for pressing the paper is 
provided between the print head 1 and a top cover 3 provided at the upper 
part of print head 1. This bail roller 4 moves in the direction indicated 
in the figure to cause the paper running toward the direction of arrow 
mark A to move toward the direction of arrow mark B and then exhaust the 
paper from the aperture 3a. 
A sound insulation material 7 is provided at a part other than the 
neighborhood of bail roller 4 of the top cover 3. 
In the printer having such structure, the impact noise of print head is 
suppressed by the sound insulation material 7 of the top cover 3 as much 
as not leaking to the front side of printer. 
On the other hand, in the horizontal type printer as shown in FIG. 1(b), an 
aperture 3 which is designed as the exhaust port of paper is provided in 
the left side of platen 2 and the print head 1 is provided at the lower 
part of platen 2. The cut sheet (SP) from the guide 6 or the continuous 
sheet (LP) transferred by the tractor 5 is transferred almost horizontally 
and exhausted forward from the aperture 3a provided at the front side of 
apparatus after completing the printing by the print head. 
In the printer as shown in FIG. 1(a), since the aperture 3a is provided at 
the upper part of platen 2, the printing result on the paper exhausted 
therefrom can be checked easily. However, the print head 1 is provided at 
the lower part of the top cover 3 to result in the problem that it becomes 
near the cover aperture 3a, noise of print head 1 leaks easily therefrom 
and resultant forward noise becomes high level. 
Moreover, since a movable bail roller 4 is provided above the print head 1, 
the sound insulating material 7 is not provided to this part of the top 
cover 3. Accordingly, sufficient sound insulation effect by the top cover 
3 cannot be obtained in this case, resulting in a problem that the forward 
noise level cannot be lowered. 
In the case of a printer shown in FIG. 1(b), the aperture 3a is provided at 
the front area of apparatus and the print paper is exhausted with the 
printing (front) side placed rear side. Therefore, it is difficult to 
check the printing result. In addition, the forward noise level is high 
because the impact noise of print head 1 is released forward in direct. 
From the point of view of a kind of paper to be used, thickness and 
rigidity are different from the paper to paper in accordance with a kind 
of paper. Therefore, a printer as shown in FIG. 1(a), FIG. 1(b) having the 
one exhaust path and the one exhaust direction cannot realize smooth 
transfer of paper for every kind of paper without occurrence of sheet 
jamming and improper line feeding. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to improve a printing apparatus 
which suppresses forward print noise while keeping the condition to easily 
check the printed paper. 
It is another object of the present invention to improve a printing 
apparatus which smoothly transfer and exhaust a variety of media. 
These objects can be achieved by executing following procedures (1) to (5). 
(1) An aperture is provided to the upper part of platen, while the print 
head to the lower part of platen and a platen is arranged between the 
aperture and print head. 
(2) A sound absorbing material or sound insulating material is provided at 
the inner surface of cover having the aperture. 
(3) A stationary type bail roller is provided above the print head. 
(4) A plurality of exhaust ports in different exhausting direction are 
provided selectably depending on the type of medium by an operator. 
(5) The members forming a plurality of exhaust ports in different 
exhausting direction are provided movably to switch the exhaust port 
depending on movement of the member. 
Namely, the print head is provided at the lower part of platen and 
therefore becomes far from the aperture at the upper part of platen. 
Thereby, leak of noise of print head from the aperture can considerably 
reduced. Moreover, since the platen is provided between the aperture and 
print head, the platen shows the effect as the sound insulating member and 
the noise generated by print head is not leaked in direct. 
In addition, leak of noise can further be reduced due to the effect of 
sound absorbing member or sound insulating member provided at the internal 
surface of cover. 
Furthermore, it is no longer necessary to acquire the moving area of bail 
roller by providing stationarily the bail roller and more sound absorbing 
members or sound insulating members may be provided at the internal 
surface of cover. 
On the other hand, since a plurality of exhaust ports are provided 
selectably depending on the type of media, the optimum exhaust path can be 
selected depending on the medium and the medium can be transferred and 
exhausted most smoothly. Therefore, forms jamming or improper line feeding 
can be prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of the present invention will be explained with 
reference to the drawings from FIG. 2 to FIG. 14. 
The like elements are designated by the like reference numerals throughout 
the drawings. 
First embodiment: 
FIG. 2.about.FIG. 5 are diagrams for explaining structure and operations of 
the first embodiment. 
FIG. 2 shows schematically the arrangement of platen 2, aperture 3a of the 
top cover 3 and print head 1 in the printing apparatus. In FIG. 2, the top 
cover 3 having the aperture 3a is provided above the platen 2 and the 
print head 1 formed by the dot print head is provided with deflection 
below the platen 2. The print head 1 is located at the position rotated 
counter-clockwise by 60.degree. around the axis of platen 2 from the 
horizontal plane including the axis of platen 2 or 30.degree. relative to 
a vertical axis. 
FIG. 3 shows schematically a structure of the first embodiment of the 
present invention. In FIG. 3, the tractor 5 is provided horizontally for 
making easier the setting of continuous sheet and a sheet guide 9b is 
provided between the platen 2 and the tractor 5. A cut sheet guide 6 is 
provided with deflection above the platen 2 and a sheet guide 9a is 
provided between the platen 2 and the cut sheet guide 6. Moreover, a sheet 
guide 9c is also provided between the print head 1 and platen 2 and an ink 
ribbon mechanism 8 is further provided to the print head 1. At the upper 
part of print head 1, the bail roller 4 is stationarily provided. 
Meanwhile, a front cover 10 is provided with inclination in the front side 
of apparatus along the print head 1 and ink ribbon mechanism 8. The front 
cover 10 has the sound insulating material 7 at the internal surface 
thereof and can be opened by rotation around the fulcrum provided at the 
lower side thereof. 
FIGS. 4(a), 4(b) show schematically a structure of top cover 3. The top 
cover 3 is provided, as shown in FIG. 4(b), with a guide rib 30 and a 
guide plate 31 for guiding the paper. The aperture 3a is provided at the 
upper surface of top cover 3 and the paper is exhausted through this 
aperture 3a. As shown in FIG. 4(a), a sound absorbing or insulating 
material 7 formed by sponge or rubber plate is provided between the guide 
ribs 30. 
As shown in FIGS. 2 and 3, the print head 1 is provided in a line with the 
aperture 3a through the platen 2. Therefore, the print head 1 is separated 
from the aperture 3a and the platen 2 provided works as the sound 
insulating material. Thereby direct leak of noise to outside can be 
prevented. 
Moreover, the side surface of print head 1 is covered with the sound 
insulating material 7 of the front cover 10 and leak of noise through the 
front cover 10 can be alleviated. Release of noise from the aperture 3a 
and the periphery thereof can be prevented by the sound insulating 
material 7 provided to the top cover 3. 
Operations of the first embodiment will then be explained with reference to 
FIGS. 3 and 5. 
In the case of executing the printing on the cut sheet, a cut sheet guide 6 
is erected first obliquely as shown in FIG. 3. The cut sheet is inserted 
along the cut sheet guide 6 and is wound around the platen 2 by the paper 
guides 9a, 9c. The printing is carried out on the cut sheet with space 
movement of the print head 1. After the printing, the cut sheet 
transferred along the platen 2 by the bail roller 4 and guide rib 30 of 
top cover 3 and is exhausted from the aperture 3a of the top cover 3. 
Therefore, the cut sheet has converted its running direction for about 
180.degree.. 
On the other hand, in the case of a continuous sheet, as shown in FIG. 5, 
the cut sheet guide 6 is rotated in horizontal and it is used as the 
stacker. Namely, the continuous sheet being set to the tractor 5 is guided 
to the platen 2 along the sheet guide 9b and the printing is carried out 
with the space movement of print head 1. The continuous sheet having 
completed the printing is transferred along the platen 2 by the bail 
roller 4 and guide rib 30 of top cover 3, exhausted from the aperture 3(a) 
of cover and is stacked by the paper guide 6. 
Therefore, the continuous sheet has converted its running direction for 
about 120.degree.. 
As described above, since the print head 1 is provided in the printing 
apparatus at the area below the platen 2, replacement of ink ribbon 8 and 
replacement of print head 1 at the time of maintenance cannot be done 
effectively. Therefore, in order to improve the efficiency of replacement 
of these elements, the front cover 10 is provided with inclination as 
shown in FIG. 5 and it can be opened by rotation thereof around the 
fulcrum at the lower side (not illustrated). 
Second embodiment: 
In view of further lowering the level of noise generated from the aperture 
3(a) of the top cover 3, the aperture area must be further reduced. The 
second embodiment has reduced the area of the aperture by optimizing the 
shape of guide rib provided at the internal surface of top cover. 
The sheet is guided by the sheet guide 9c in such a manner as being wound 
around the platen 2 for the printing. After the printing, the sheet is 
then transferred to the aperture 3a while it is pressed toward the platen 
2 with the pair of bail rollers which are usually provided with a proper 
space. In this case, a part of the sheet passing through the inside of the 
pair of bail rollers 4 is transferred to the aperture 3(a), under the 
condition indicated by A, along the platen 2 as shown in FIG. 6. However, 
a part of the sheet passing through the outside of the pair of bail 
rollers 4 is transferred to the aperture 3(a) facing to the direction 
different from A under the condition that when the part is nearer to both 
ends of the sheet, it is gradually separated from the platen 2 and it is 
most separated from the platen as shown by B. Therefore, in the case of 
the guide rib 30 in the uniform shape as shown in FIG. 4(b), since the 
both sides of sheet shown by B in FIG. 6 must be exhausted from the 
aperture 3(a) for the reliable exhaustion of the sheet under the condition 
mentioned above from the aperture 3(a), the slot width of aperture 3(a) 
must sufficiently be large. As a result, the noise released becomes higher 
in level as much as enlargement of slot width. 
FIG. 7 is a perspective view schematically indicating the internal surface 
of top cover 3 providing a plurality of guide ribs 30 of the present 
invention. In FIG. 7, a plurality of guide ribs 30a, 30b, 30c, 30d, . . . 
, 30k, 301 are provided in parallel with the predetermined pitch in the 
axial direction of the platen 2. The envelope of guide ribs for guiding 
the papers (the surface including a curve S indicated by a chain line and 
a side T of the aperture 3a) is designed so that it becomes nearest to the 
platen 2 at the guide ribs 30f.sub.1, 30f.sub.2, 30f.sub.3 near the center 
corresponding to the area between two bail rollers 4 and is gradually 
separated from the platen 2 while it moves to the guide rib 30a from 30e 
and to 301 from 30g. 
In case the top cover 3 providing the guide ribs of the shape shown in FIG. 
7 is used, the center area of sheet is guided by the guide ribs 30f.sub.1, 
30f.sub.2, 30f.sub.3 and both sides of sheet are sequentially guided by 
the guides ribs from 30e to 30a and from 30g to 301. As a result, both 
sides of sheet corresponding to guide ribs from 30e to 30a and from 30g to 
301 are also guided in the same direction as the center area corresponding 
to the guide ribs 30f.sub.1, 30f.sub.2, 30f.sub.3 and is reliably 
exhausted from the aperture 3a as indicated by the arrow mark. Therefore, 
the aperture can be reduced in area in comparison with the case where the 
guide ribs of the uniform shape are used. 
Third embodiment: 
In case the printing is carried out on the special paper such as an 
inflexible cut sheet, directional conversion of 180.degree. around the 
platen 2 gives adverse effect on the printing result. Therefore, as shown 
in FIG. 8, the mechanism is provided so that the top cover 3 can be opened 
by rotating around the axis at the rear end of cover 3. This mechanism is 
illustrated in FIGS. 9(a) and 9(b). 
FIG. 9(a) shows schematically a side elevation of the top cover 3, while 
FIG. 9(b) shows a sectional view along the line A--A of FIG. 9(a). The top 
cover 3 is so structured as can be rotated around the rotating axis 40 for 
the main body frame 11 and has a protrusion 41 which is engaged with a 
protrusion 80 of the main body frame 11. FIGS. 10(a), 10(b) are 
perspective views of top cover 3 of the printing apparatus of the third 
embodiment. In case the printing is carried out on the ordinary paper, the 
top cover 3 is closed as shown in FIG. 10(a). In this case, since the main 
body frame 11 is formed by a mold material, an engaging protrusion 41 of 
the top cover 3 can easily be set to the engaging position, as shown in 
FIGS. 9(a) and 9(b) by deflecting the mold protrusion 80 of the main 
bodyframe 11. When the top cover 3 is being closed, the exhaust port 3b 
shown in FIG. 8 is shut and the paper is guided by the guide rib 30 (not 
illustrated) provided at the internal surface of top cover 3 and is 
exhausted upward in the direction U from the exhaust port 3a. 
When the top cover 3 is opened, the engaging protrusion 41 of the top cover 
3 can easily be positioned above the mold protrusion 80 as shown in FIG. 
9(b) by deflecting the mold protrusion 80 of the main body frame 11. This 
condition is also shown in FIG. 10(b). When the top cover 3 is opened, the 
ex-haust port 3(b) is formed in place of the exhaust port 3(a) as shown in 
FIG. 8, the sheet is not guided by the guide rib 30 (not illustrated) 
provided at the internal surface of top cover 3 and therefore it does not 
run along the platen 2 and is exhausted in the direction of arrow mark F 
between the top cover 3 and the bail roller 4. Accordingly, a curvature of 
inflexible sheet becomes small and smooth exhaustion of paper is carried 
outgiving no adverse effect on line feeding during the printing. However, 
in this case, the sound insulation effect by arrangement of print head 1 
and cover 3 can be a little deteriorated. 
FIG. 11 is a perspective view of the housing and mechanism of the printing 
apparatus to which the present invention is applied. 
Fourth embodiment: 
The fourth embodiment provides a pair of apertures as the sheet exhaust 
ports and this embodiment has a structure that any one desired is selected 
depending on the type of sheet. The structure and operations are explained 
with reference to FIGS. 12(a), 12(b) and 12(c). FIG. 12(a) shows 
schematically a structure of the fourth embodiment. In this embodiment, a 
slidable switching member 33 is provided at the upper part of platen 2 to 
form selectably the pair of exhaust ports 3(a), 3(b). As shown in FIG. 
12(b), when the switching member 33 moves to the left side, the exhaust 
port 3(b) is closed and the exhaust port 3(a) is formed. Accordingly, the 
ordinary paper is guided by the guide rib provided to the switching member 
33 and is then exhausted from the exhaust port 3(a). 
Meanwhile, if the paper-stapled sheet is exhausted from the aperture 3(a) 
as shown in FIG. 12(b), it is wound around the platen 2, generating layer 
dislocation between the sheet in the side of the platen 2 and the sheet in 
the opposite side. In order to prevent such event, the exhaust port 3(a) 
is shut and the exhaust port 3(b) is formed by moving the switching member 
33 to the right side as shown in FIG. 12(c). As a result, the 
paper-stapled sheet path is formed like the alphabet S. Namely, the sheet 
has been bent along the platen 2 after the bail roller 4 but exhausted 
from the exhaust port 3(b) through the opposite bending from that by the 
platen 2. Since the sheet path is formed like an alphabet S, layer 
dislocation can be prevented. 
Here, it is enough that the switching member 33 is formed to be slidable 
for the main body frame 11. For instance, it is recommended that a part of 
the switching member 33 engages with the guide groove of the main body 
frame 11 so that it can slide along the guide groove. 
Fifth embodiment: 
This embodiment proposes a structure that two kinds of exhaust ports can be 
formed by sliding the top cover of the printing apparatus. 
FIG. 13(a) is a perspective view of the fifth embodiment and FIG. 13(b) is 
a structural diagram of the fifth embodiment. FIG. 14(a) is a plan view 
observed from the direction B of FIG. 13(a); FIG. 14(b) is a partial side 
elevation observed from the direction C of FIG. 13(a); and FIGS. 14(c), 
14(d) are sectional views along the line D--D of FIG. 14(b). 
In FIG. 13(b), the front cover 10c can slidable in vertical for the main 
body frame 11. In case the front cover 10c is located at the lower 
position, the first aperture 3(a) is formed and when the front cover 10c 
is located at the upper position (indicated by a chain line), the second 
aperture 3b is formed. In FIGS. 14(a), (b), (c), (d), a guide rail 81 
having an engaging protrusion 81a at the intermediate area thereof is 
provided to the main body frame 11, and meanwhile a guide groove 42 which 
engages with the guide rail 81 is provided to both side surfaces of the 
front cover 10c. 
In case the printing is carried out on an ordinary sheet, the front cover 
10c is lowered as shown in FIGS. 13(a), 13(b). In this case, the guide 
groove 42 of the front cover 10c is guided to the lowest part, sliding 
over the engaging protrusion 81a, along the guide rail 81 of the main body 
frame 11 as shown in FIG. 14(d). When the front cover 10c is lowered, the 
second aperture 3b is closed as shown by a solid line of FIG. 13(b), 
leaving only the first exhaust port 3(a) and the sheet is exhausted from 
the first aperture 3(a). 
On the other hand, in case the printing is carried out on a thick sheet or 
inflexible sheet, the front cover 10c is moved upward by sliding as 
indicated by a chain line in FIG. 12(b). In this case, as shown in FIG. 
14(c), the guide groove 42 of the front cover 10c is positioned and 
stopped sliding over the engaging protrusion 81a along the guide rail 81 
of the main body frame 11. When the front cover 4c is moved upward by the 
sliding, the second exhaust port 3b is formed as indicated by the chain 
line of FIG. 13(b). Therefore, the thick sheet or inflexible sheet is not 
wound around the platen 1, guided to the second aperture 3(b) from the 
print head 2 and is exhausted from the exhaust port 3(b). 
In the third and fourth embodiments, the switching member is rotated or 
moved by sliding to form the aperture for exhausting the sheet, but a 
method, for example, removal of the switching member itself can also be 
employed. 
Moreover, the exchange of two exhaust ports(aperture) has been explained 
but the exchange among three or more exhaust ports is also applicable. 
The printing mechanism is not limited only to the serial dot printing head 
and the other printing mechanism such as the line impact print head, so 
long as it is an impact type, can also be used.