Recording device
BACKGROUND OF THE INVENTION
1. Field of Invention
[0001]
The present invention relates to a recording device having an optical sensor paper for detecting if recording paper is present when the carriage travels in the main scanning direction of the recording head.
2. Description of Related Art
[0002]
Printers and other recording devices of the related art have an optical paper width detection sensor for detecting the width of the paper in the main scanning direction of the recording head mounted on a carriage when recording an image or text on the recording paper. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-H06-293163. This optical paper width detection sensor detects if paper is present by emitting a light beam and then differentiating the intensity of the light reflected from the recording paper and the intensity of the light reflected from the surface of the typically black surface of the paper guide or platen. More specifically, when white recording paper is inserted between the emitter and the paper guide, a strong reflection is sensed by the photodetector and paper is determined to be present. When the paper is not inserted, however, the reflection from the black guide surface detected by the photodetector is weak and paper is determined to not be present. [0003]
When recording paper is conveyed through a printer or other such recording device, friction between the paper and the guide surface produces paper dust and chaff. When this dust collects on the guide surface of the paper guide in the
recording device of the related art described above, the light emitted from the optical paper width detection sensor hits the paper dust, which is the same color as the recording paper, the reflection is therefore strong, and the paper presence or paper width may be erroneously detected.
SUMMARY OF THE INVENTION [0004]
The recording device according to the present invention is directed to the foregoing problem of the related art, and enables more accurate detection of the recording paper. [0005]
A first aspect of the invention is a recording device having a carriage that carries a recording head and moves in a scanning direction, and a paper guide that forms a guide surface that guides recording paper conveyed between the carriage and paper guide. An optical detection sensor that detects the presence of recording paper based on reflection of light emitted to the recording paper is disposed to the carriage, and an inclined surface is formed from the guide surface of the paper guide on the side opposite the optical detection sensor at a different angle than the printing surface of the conveyed recording paper.
When light emitted from the optical detection sensor mounted on the carriage is incident to the recording paper, the incident light is reflected to the detection sensor. When the emitted light is incident to the inclined surface of the paper guide, however, the reflected light is not reflected to the detection sensor. Whether the recording paper is present or not can therefore be detected more reliably from the detection of the reflected light.
Preferably, an opening that opens to below the inclined surface is disposed to the paper guide. This enables
discharging the paper dust from the opening, thus making collectior of paper dust on the inclined surface difficult. This also reduces the possibility of sensor detection errors caused by scattered reflection of light by paper dust accumulated on the inclined surface, depending on differences in the performance of the sensor. [0006]
Further preferably, the opening is formed in the paper guide to a part of the guide surface to which light from the optical detection sensor is incident.
In this aspect of the invention light emitted from the optical paper detection sensor will not be reflected by the paper guide, and the presence of recording paper can therefore be detected more reliably based on the detection of reflected light. [0007]
Yet farther preferably, the inclined surface and opening are formed continuously along the scanning direction of the recording nead.
This aspect of the invention enables detecting the paper width of tne recording paper or the presence of recording paper at any position along the scanning direction. [0008]
In another aspect of the invention the inclined surface is formed at an angle enabling paper dust to descend of its own weight along the incline to below.
In this aspect of the invention paper dust produced from conveying the recording paper is discharged from the opening by moving downward of its own weight along the inclined surface. Collection of paper dust on the inclined surface is thus inhibited, and detection errors by the optical detection sensor can be eliminated. [0009]
In another aspect of the invention the optical detection sensor is a paper width detection sensor for detecting the width of the recording paper.
This aspect of the invention enables confirming the presence of recording paper on the guide surface, and thus enables more reliably detecting the paper width. [3010]
By rendering an inclined surface from the guide surface of the paper guide on the side opposite the optical detection sensor at a different angle than the printing surface of the conveyed recording paper, light emitted from an optical paper width detection sensor for detecting the paper width that is incident to the inclined surface of the paper guide is not reflected to the detection sensor. Whether or not the recording paper is present can therefore be detected more reliably by detecting the presence of reflected light. The width of the recording paper and whether recording paper is present can therefore be detected more accurately, and the reliability of the recording device is thus improved.
Furthermore, because paper dust produced from conveying the recording paper moves along the incline and is discharged from the opening, accumulation of paper dust on the incline is inhibited, and the possibility of detection errors by the optical paper width detection sensor is reduced. Maintenance to remove paper dust from the guide surface is also needed less freguently, and user convenience is thus improved.
The foregoing effect is achieved most easily by rendering an opening at the position where the light from the optical detection sensor is omitted.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a
DESCRIPTION OF PREFERRED EMBODIMENTS [0011] * Embodiment 1
A first embodiment of the invention is described next with reference to the accompanying figures.
FIG. 1 is an external oblique view from the front of a printer 10 according to this embodiment of the invention, FIG. 2 is a side section view of the printer 10, and FIG. 3 and FIG. 4 are oblique views showing the frame of the printer 10.
The printer 10 is a serial dot impact printer that has a dot impact recording head 20 that selectively drives a plurality of wire dots, and a carriage 21 on which the recording head 20 is mounted. The printer 10 prints images, including text, by driving the wires of the recording head 20 to transfer ink to the recording paper (referred to below as a sheet P, see FIG. 8).
As shown in FIG. 2, the printer 10 has a printer unit 12 rendering the recording unit, a tractor unit 13, and a sheet guide 14, which are covered on top and bottom by an upper case 15 and a lower case 16 as shown in FIG. 1. The sheet P could be cut-sheet paper of a predetermined length, or continuous paper of multiple connected sheets. Cut-sheet paper includes, for example, invoice forms, multipart forms, ledger pages, and cut film. Continuous paper includes fan-fold paper, for example.
The printer unit 12 has a recording mechanism unit including the recording head 20, carriage 21, and a flat platen 22, and a plurality of transportation rollers 23 as the
sheet transportation mechanism unit. More particularly, the printer unit 12 has a back frame 27, the flat platen 22, a carriage shaft 28, a plurality of roller shafts 23a, and the tractor unit 13 disposed between a pair of side frames (left side frame 25 and right side frame 26). The carriage 21 is movably attached to the carriage shaft 28, and the transportation rollers 23 are disposed to the roller shafts 23a. [0012]
The transportation rollers 23 are disposed in top and bottom pairs in the front and back of the printer unit 12 relative to the flat platen 22 (some of the transportation rollers 23 are not shown), and are driven rotationally clockwise and counterclockwise as seen in FIG. 2 by means of a sheet transportation motor not shown and a drive wheel train 41 that is disposed on the outside of the right side frame 2 6 and is connected to the motor. This enables conveying the sheet P from the front (the sheet guide 14 side) of the printer un.it 12 to the back, or from the back of the printer unit 12 to the front. The sheet P travels in a sub-scanning direction perpendicular to the main scanning direction of the carriage 21. [0013]
The carriage 21 is slid onto and slides freely along the carriage shaft 28, carries the recording head 20, and is connected to a timing belt 48 (see FIG. 3) that is driven by a carriage drive motor (not shown), which is a stepping motor in this embodiment of the invention.
By driving the carriage drive motor forward or reverse, the carriage 21 can therefore be driven by the timing belt 48 along the carriage shaft 28 in the main scanning direction, which is parallel to the carriage shaft 28 and aligned with the long side of the flat platen 22. The recording head 20 has

a plurality of dot wires (not shown in the figure), and impels
the wires toward the flat platen 22 to print.
[0014]
As shown in FIG. 5, a stationary ink ribbon cartridge 29 is removably installed to the printer unit 12 so that the ink ribbon of the ink ribbon cartridge 2 9 is between the recording head 20 and the flat platen 22.
As a result, when the recording head 20 and carriage 21 travel in the main scanning direction and the dot wires are impelled to strike the ink ribbon, ink from the ink ribbon is transferred to the sheet P conveyed between the flat platen 22 and the recording head 20 and an image, including text, is recorded on the sheet P. As also shown in FIG. 3, a ribbon mask holder 51 is also disposed to the carriage 21. The ribbon mask holder 51 prevents contact between the ink ribbon pulled out from tne ink ribbon cartridge 29 and the sheet P (cut-sheet paper or continuous paper) conveyed against the surface of the flat platen 22. [0015]
The tractor unit 13 supplies continuous paper to the sheet transportation mechanism unit, and as shown in FIG. 4 has a pair of left and right tractors 30.
As shown in FIG. 2, each tractor 30 has a tractor drive pulley 30a, a tractor idler pulley 30b, and a tractor belt 31 that is mounted on the tractor drive pulley 30a and tractor idler pulley 30b. A drive mechanism not shown rotationally drives the tractor drive pulley 30a, which drives the tractor belt 31 and conveys the continuous paper.
The recording operation of the recording head 20 is achieved by repeating a sequence of operations that print one line by selectively driving the dot wires of the recording head 20 while the recording head 20 is moved by the carriage 21 in the main scanning direction, and then drive the
transportation rollers 23 (and tractor unit 13) as the sheet transportation mechanism unit to convey the continuous paper a prescribed distance after completing each line. [0016]
FIG. 6 is an oblique view of the carriage 21, and FIG. 7 is an oblique view of the ribbon mask holder 51 disposed to the carriage 21.
A boss 19a through which the carriage shaft 28 is inserted to slide freely is formed in unison to the carriage 21 so that the carriage 21 is guided by the carriage shaft 28 and is driven axially to the carriage shaft 28 in the main scanning direction.
The ribbon mask holder 51 is attached to the carriage 21 as described above by means of a guide pin 52. [0017]
As shown in FIG. 6 and FIG. 7, a paper width detection sensor 43 (an optical sensor) for optically detecting the width of t.he sheet P (cut-sheet paper) is disposed to the right side (as seen in the figure) of the base 51a of the ribbon mask holder 51.
The paper width detection sensor 43 is a reflective optical sensor that has an emitter and a receptor not shown adjacently disposed in the main scanning direction of the carriage 21. As shown in FIG. 8 and FIG. 9 the emitter and receptor are disposed in opposing positions above and below the guide surface 45a of the paper guide 45.
The paper guide 45 is disposed below the recording head 20 mounted on the carriage 21 on the downstream side of the flat platen 22 in the sheet transportation direction (on the right side in FIG. 2 and to the inside of the flat platen 22 in FIG. 5) . The guide surface 45a, which is the top surface of the paper guide 45, guides the conveyed sheet P to the downstream side in the transportation direction. As shown in
FIG. 5, the paper guide 45 extends along the main scanning direction of the recording head 20, and supports the full width of the conveyed sheet P from below. The sides of the paper guide 45 are affixed to the left side frame 25 and right side frame 26. [0018]
An incline 45b extending along the main scanning direction and a paper chaff discharge window 46 (opening) are formed in the guide surface 45a of the paper guide 45. When the carriage 21 scans in the main scanning direction, the paper widtn detection sensor 43 emits a detection beam toward this guide surface 45a or the printing surface of the sheet P conveyed over the incline 45b. [0019]
FIG. 3 is a section view of the paper guide 45 perpendicularly to the main scanning direction, and FIG. 9 is the same section view when a sheet P is conveyed over the paper guide 45 shown in FIG. 8. Note that in FIG. 8 and FIG. 9 the left side of the figure is the upstream side in the cur-sheet transportation direction and the right side is the downstream side, and the main scanning direction of the recording lead 20 is perpendicular to the surface of the drawing.
As shown in FIG. 8, an incline 45b is provided on both the upstream and downstream sides in the transportation direction, and slope down at a specific angle A to the substantially flat guide surface 45a. Because the guide surface 45a and the surface of the sheet P are substantially parallel, the inclines 45b also slope at angle A to the printing surface of the sheet P (see FIG. 9). [0020]
When the sheet P passes this part of the guide surface 45a, friction with the guide surface 45a produces paper dust
47, which drops onto the guide surface 45a and the inclined surfaces 45b. As a result, the inclination angle A of the inclines 45b is set so that the paper dust 47 does not collect on the inclines 45b and instead drops along the inclines 45b into the paper chaff discharge window 46 therebelow due to the weight of the paper dust 47 or vibration of the printer 10 or movement of the carriage 21 when printing.
The paper chaff discharge window 46 is formed below both of the inclines 45b, and is a long hole with the long axis in the main scanning direction. The paper dust 47 that drops along the inclines 45b described above falls through the paper chaff discharge window 46 and is discharged below the paper guide 45. The light L output from the emitter of the paper width detection sensor 43 disposed to the ribbon mask holder 51 is directed to this paper chaff discharge window 46. This light L passes through the paper chaff discharge window 46 to below, and the reflected light R is therefore not incident to the receptor unit of the paper width detection sensor 43. [0021]
When a sheet P is conveyed over the guide surface 45a, the light 1 output from the emitter of the paper width detection sensor 43 is incident substantially perpendicularly to the printing surface of the sheet P, is reflected by the printing surface, and the reflected light R is thus detected by the receptor of the paper width detection sensor 43 as shown in FIG. 9. [0022]
The paper guide 45 can be manufactured by first forming a slit lengthwise in an elongated steel plate and then using a press to form the inclines 45b as shown in FIG. 8. The paper guide 45 can also be formed by combining two separate parts, an upstream side part and a downstream side part. The paper guide 45 can also be molded from plastic with the guide
surface 45a and inclines 45b rendered formed in unison with the paper guide 45.
If the paper chaff discharge window 46 is formed continuously along the long axis, the strength of the paper guide 45 may be reduced and vibration could cause the paper guide 45 to chatter. The paper chaff discharge window 46 can therefore alternatively be rendered from a plurality of holes spaced along the long axis. Further alternatively, a support member (not shown in the figure) that supports the paper guide 45 from below can be provided separately to the side frames 25 and 26 in order to prevent chatter in the paper guide 45.
In addition, by making the guide surface 45a and inclines 45b of the paper guide 45 black, the reflection therefrom will be weak, and the light from the paper width detection sensor 43 will be diffusely reflected so that it will not enter the receptor and detection errors can be prevented. [0023]
By thus forming inclines 45b that slope from the guide surface 45a of the paper guide 45 at a different angle A to the printing surface of the conveyed sheet P in this embodiment of the invention, paper dust 47 moves along these inclines 45b and is discharged from the paper chaff discharge window 46, and the paper dust 47 therefore cannot easily collect on the inclined surfaces 45b. Maintenance to clean the paper dust from the guide surface is thus required less frequently, and ease of use is improved. [0024]
Furthermore, because the light emitted from the paper width detection sensor 43 is directed toward the paper chaff discharge window 46, the reflected light R is not incident to the receptor of the paper width detection sensor 43. On the other hand, when a sheet P is conveyed over the paper guide 45, the reflected light R enters the receptor of the paper
width detection sensor 43. Because the incidence of reflected light R on the receptor is thus determined by the presence of a sheet P, the paper width detection sensor 43 can detect the width of the sheet P. The width of the sheet P can therefore be detected more reliably, and the reliability of the recording device is improved. [0025]
In addition, because the angle of inclination A of the inclines 45b is set so that the paper dust 47 falls down along the inclines 45b into the paper chaff discharge window 46 therebelow due to the weight of the paper dust 47 or vibration of the printer 10 when printing, it is more difficult for the paper dust 47 to collect on the inclined surfaces 45b. Detection errors caused by random reflection of the light from the paper width detection sensor 43 by the accumulated paper dust can therefore be prevented. [0026]
A first embodiment of the invention is described above but the invention is not limited to this embodiment and can be varied in many ways based on the technical concept of the invention.
The first embodiment is described using a serial dot impact printer as an example of the recording device of the invention, but the invention can be applied to thermal printers, Inkjet printers, and other types of printers by disposing an optical detection sensor to the recording head and detecting the presence of paper by means of the reflected light. The likelihood of paper detection errors caused by paper dust when conveying the paper can therefore be reduced. [0027]
This first embodiment describes a paper width detection sensor 43 for detecting the width of a sheet P as the optical detection sensor, but the invention is not limited to
detecting paper width. The optical detection sensor can be used, for example, as a sensor for simply detecting if a sheet P is present based on the reflected light R. [0028]
The printer 10 according to this first embodiment of the invention is also described as having a flat platen 22, but can be rendered in the same way with a round platen instead to more reliably detect the paper width and/or presence of a sheet P. [0029] * Embodiment 2
A second embodiment of the invention is described next with reference to FIG. 10. This second embodiment of the invention changes the inclines 45b and the paper chaff discharge window 46 of the first embodiment, but is otherwise identical to the first embodiment.
FIG. 10 is a section view of the paper guide 45 perpendicularly to the main scanning direction, and thus corresponds to the view shown in FIG. 8 of the first embodiment. In this second embodiment of the invention the bottom end 150 of one incline 145b (the inclined surface on the upstream side in FIG. 10) extends to a point below the bottom end 151 of the other incline 45b.
The paper chaff discharge window 14 6 is formed by the horizontal opening between the bottom ends 150 and 151, and is an elongated hole with the long axis aligned with the main scanning direction. Paper dust 47 that drops along the incline 145b falls through the paper chaff discharge window 146 and is discharged below the paper guide 145. Paper dust 47 that descends along the incline 45b falls onto the other incline 145b and then falls through the paper chaff discharge window 14 6 and is discharged below the paper guide 145. [0030]
The J ight L emitted from the emitter of the paper width detection sensor 43 mounted on the ribbon mask holder 51 is directed to the incline 145b. This light L emitted from above strikes the incline 145b and the reflected light R is reflected at a reflection angle A that is equal to the incidence angle A, these angles being symmetrical to the axis X perpendicular to the incline 145b. As a result, the reflected light R does not enter the receptor of the paper width detection sensor 43. [0031]
However, when a sheet P is conveyed over the guide surface 145a, the light L output from the emitter of the paper width detection sensor 43 is substantially perpendicularly incident to the printing surface of the sheet P, is reflected by the printing surface, and the reflected light R thus enters the receptor of the paper width detection sensor 43. Because the incidence of reflected light R on the receptor is thus determined by the presence of a sheet P, the paper width detection sensor 43 can be used to detect the paper width. [0032]
By thus forming an incline 145b from the guide surface 145a of the paper guide 145 sloping at a different angle A to the printing surface of the conveyed sheet P in this second embodiment of the invention, paper dust 47 moves along the incline 14 5b and is discharged from the paper chaff discharge window 146, and the paper dust 47 therefore cannot easily collect on the inclined surface 145b. Maintenance to clean the paper dust from the guide surface is thus required less frequently, and ease of use is improved. [0033]
Furthermore, because the light emitted from the paper width detection sensor 43 is directed toward the incline 145b with a slope of angle A, the reflected light R is not incident
to the receptor of the paper width detection sensor 43 when a sheet P is not on the paper guide 145. On the other hand, when a sheet P is conveyed over the paper guide 145, the reflected light R enters the receptor of the paper width detection sensor 43. Because the incidence of reflected light R on the receptor is thus determined by the presence of a sheet P, the paper width detection sensor 43 can detect the width of the sheet P. The width of the sheet P can therefore be detected more reliably, and the reliability of the recording device is improved. [0034]
In addition, because the angle of inclination A of the incline 145b is set so that the paper dust 47 falls down along the incline 145b into the paper chaff discharge window 146 therebelow due to the weight of the paper dust 47 or vibration of the printer 10 when printing, it is more difficult for the paper dust 47 to collect on the inclined surface 145b. Detection errors caused by random reflection of the light from the paper width detection sensor 43 by the accumulated paper dust can therefore be prevented. [0035]
This second embodiment of the invention can also be rendered without providing the guide surface 145a positioned on the downstream side shown in FIG. 10. In this case the bottom end 150 of the incline 145b is the opening rendering the paper chaff discharge window 14 6.
In addition, by making the guide surface 145a and incline 14 5b of the paper guide 45 black, the reflection therefrom will be weak, and the light from the paper width detection sensor 43 will be diffusely reflected so that it will not enter the receptor and detection errors can be prevented.
This second embodiment is described using a serial dot impact printer as an example of the recording device of the

invention, but the invention can be applied to serial thermal printers, Inkjet printers, and other types of printers.
A stepping motor is also used to drive the carriage 21, but a dc motor can be used instead.
The invention being thus described, it will be obvious that it may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of tne following claims.

We Claim:
1. A recording device comprising:
a carriage that carries a recording head and moves in a scanning direction; and
a paper guide that forms a guide surface that guides recording paper conveyed between the carriage and paper guide;
wherein an optical detection sensor that detects the presence of recording paper based on reflection of light emitted to the recording paper disposed to the carriage; and
an inclined surface is formed from the guide surface of the paper guide on the side opposite the optical detection sensor at a different angle than the printing surface of the conveyed recording paper.
2. The recording device described in claim 1, further
comprising:
an opening that opens to below the inclined surface is disposed to the paper guide.
3. The recording device described in claim 2, wherein the opening is formed in the paper guide to a part of the guide surface to which light from the optical detection sensor is incident.
4. The recording device described in any of claims 1 to 3, wherein the inclined surface and opening are formed continuously along the scanning direction of the recording head.
5. The recording device described in claim 1, wherein the inclined surface is formed at an angle enabling paper dust to descend of its own weight along the incline to below.
6. The recording device described in claim 1, wherein the optical detection sensor is a paper width detection sensor foa detecting the width of the recording paper.