JPH04191235A - Sheet detector - Google Patents

Abstract

PURPOSE:To keep off any misdetection due to receiving a ray of disturbance light with certainty by installing a shading body which is set up opposite to a photodetector after reflectance on a surface being opposed to a guide member is set to a remarkably lower value than that of a sheet. CONSTITUTION:Since light emitted out of a light receiving element 8 of a reflection type photodetector 7 is reflected to a sheet 14 only at a time when where is this sheet 14 between a guide member 6 and a shading body 10 and it is incident into a light receiving element 9, it is detected that there is the sheet. In addition, since the light receiving element 9 of this photodetector 7 is always covered with the shading body 10, any misdetection due to receiving a ray of disturbance light is surely prevented from occurring.

Description

[Detailed description of the invention] Industrial applications Honbaku Town relates to sheet detection devices.

2. Description of the Related Art For example, in an office machine that transports sheets such as printing paper and manuscripts, it is necessary to detect the sheets being transported for purposes such as controlling the timing of various operations. The conventional example will be explained based on FIGS. 5 to 7. A print head 5 is mounted on a carrier 4 which is slidably held by a carrier shaft 2 parallel to the platen 1 and a guide rail 3. A paper pan 6 serving as a guide member is provided below the platen 1, and a photoelectric detector 7 is embedded in the paper pan 6. As shown in FIG. 7, this photoelectric detector 7 consists of a light emitting element 8 and a light receiving element 9, and by changing the arrangement of the light emitting element 8 and the light receiving element 9, it can be of a reflective type or a transmissive type. Here, it will be explained as a reflection type photoelectric detector. Note that the outer circumferential surface of the platen 1 is made black, for example, so as to have a reflectance extremely lower than that of the sheet.

Therefore, when a sheet is present on the outer peripheral surface of the platen 1, the light emitted from the light emitting element 8 is reflected by the sheet and reflected by the light receiving element 9, so it is detected that the sheet is present. If it does not exist, the light receiving element 9
Since a certain level of light is not incident on the sheet, it is detected that there is no sheet.

Problems to be Solved by the Invention Since the light-receiving element 9 responds to the amount of incident light, it may receive not only reflected light from the light-emitting element 8 but also disturbance light. Therefore, depending on the amount of disturbance light, there is a risk of erroneously detecting the presence or absence of a sheet.

Means for Solving the Problems The invention of claim 1 provides a guide member that supports a sheet being conveyed, a reflective photoelectric detector embedded in the surface of the guide member, and a reflective photodetector on a surface facing the guide member. and a light shielding body disposed opposite to the photoelectric detector and having a reflectance significantly lower than the reflectance of the sheet.

The invention according to claim 2 provides a guide member that supports a sheet to be conveyed, a light shielding member disposed opposite to the guide member, and a light emitting element embedded opposite to each other in a surface facing the guide member and the light shielding member. and a transmission type photoelectric detector having a light receiving element.

The invention of claim 1 provides that only when a sheet is present between the guide member and the light shielding member, the light emitted from the light emitting element of the reflective photoelectric detector is reflected by the sheet and enters the light receiving element. Therefore, it is detected that there is a sheet. Further, since the light receiving element of the photoelectric detector is always covered with a light shielding body, erroneous detection due to reception of disturbance light is reliably prevented.

In the invention of claim 2, when the sheet is present between the guide member and the light shielding member, the light directed from the light emitting element to the light receiving element is blocked by the sheet, and when the sheet is not present, the light from the light emitting element is blocked. The light is incident on the light receiving element, thereby detecting the presence or absence of the sheet.

Further, since the light receiving element is always covered by either the light shielding member or the guide member, erroneous detection due to reception of ambient light is reliably prevented.

Embodiment An embodiment of the invention of claim 1 will be explained based on FIGS. 1 to 3. Components that are the same as those described in FIGS. 5 to 7 are designated by the same reference numerals, and description thereof will be omitted. A reflective photoelectric detector 7 is embedded in the surface of the paper pan 6. In addition, the light shielding body 1 has a reflectance of the surface facing the paper pan 6 set to a significantly lower value than the reflectance of the sheet.
0 is placed opposite the photoelectric detector 7. This light shield 1
0 has a vertically long elongated hole 11 in the center, and this elongated hole 1
Both ends of the support shaft 12, which is passed through the support shaft 1, are fixed to a frame (not shown). Further, this light shielding body 10 is formed with a guide surface 13 that is inclined in a direction that gradually moves away from the paper pan 6 as it goes from the center to both ends.

In such a configuration, FIG. 2 shows a case where there is no sheet between the paper pan 6 and the light shielding body 10. In this case, the light emitting element 8 of the reflective photoelectric detector 7 emits light, but the light receiving element 9 does not react because the reflectance of the lower surface of the light shield 10 is extremely low. In other words, it is detected that there is no sheet. In addition, since the light receiving element 9 is covered with the light shielding body 10, it is not exposed to ambient light. In particular, the light shield 10
Since the light-receiving element 9 is brought into close contact with the paper burner 6 due to its own weight, the light-receiving element 9 is reliably blocked from ambient light. Therefore, it is possible to reliably prevent the error of determining that there is a sheet when there is no sheet.

Moreover, the structure for blocking disturbance light is extremely simplified.

FIG. 3 shows a state in which the sheet 14 is being conveyed, and in this case, the light shielding body 10 guides the sheet 14 through its guide surface 13 and is displaced upward according to the thickness of the sheet 4.

The light from the light emitting element 8 is reflected by the sheet 14 and enters the light receiving element 9. As a result, it is detected that the sheet 14 is present.

Next, an embodiment of the invention according to claim 2 will be described based on FIG. 4. In this embodiment, a light emitting element 8 embedded in the lower surface of a light shielding body 10 and a light receiving element 9 embedded in the surface of a paper pan 6 are made to face each other to form a transmission type charge detector 15.

In such a configuration, the paper pan 6 and the light shield 10
When the sheet 14 is conveyed between
The light from the light emitting element 8 is blocked by the sheet 14, and the light from the light emitting element 8 is blocked by the light receiving element 9 only when the sheet 14 is not present.
is incident on the Thereby, the presence or absence of the sheet 14 is detected. In addition, regardless of the presence or absence of the sheet 14, the light receiving element 9 is covered with the light shielding body 10, so that it is not affected by ambient light. The light emitting element 8 is buried in the paper pan 6,
When the light receiving element 9 is embedded in the light shielding body 10, the light receiving element 9 is shielded from ambient light by the paper pan 6.

Effects of the Invention As described above, the invention of claim 1 includes a guide member that supports a conveyed sheet, a reflective photoelectric detector embedded in the surface of the guide member, and a reflective photodetector on the surface facing the guide member. and a light shield placed opposite the photoelectric detector, the reflectance of which is set to a significantly lower value than the reflectance of the sheet, so that only when the sheet is present between the guide member and the light shield, the reflective type The light emitted from the light-emitting element of the charging detector is reflected by the sheet and enters the light-receiving element, so it is detected as there is a sheet, and the light-receiving element of the photoelectric detector is always covered with a light shielding element. This has the advantage that erroneous detection due to reception of disturbance light is reliably prevented, and the structure for blocking disturbance light is extremely simplified.

As described above, the invention of claim 2 includes a guide member that supports a sheet to be conveyed, a light shielding member disposed opposite to the guide member, and a light shielding member embedded opposite to each other in the opposing surface of the guide member and the light shielding member. Since the transmissive photoelectric detector has a light-emitting element and a light-receiving element, when a sheet is present between the guide member and the light-shielding element, the sheet blocks light traveling from the light-emitting element to the light-receiving element. When the sheet is not present, the light from the light-emitting element is incident on the light-receiving element, thereby detecting the presence or absence of the sheet, and the light-receiving element is always covered with either a light shield or a guide member. Therefore, erroneous detection due to reception of disturbance light is reliably prevented, and the structure for blocking disturbance light is extremely simplified.

[Brief explanation of drawings]

1 to 3 show an embodiment of the invention according to claim 1, in which FIG. 1 is a side view, FIGS. 2 and 3 are side views of main parts, and FIG. 4 is a side view of the main part, and FIG. 5 to 7 show a conventional example, in which FIG. 5 is a side view, FIG. 6 is a partial side view, and FIG. FIG. 2 is a circuit diagram of a photoelectric detector.

Claims (1)

[Scope of Claims] 1. A guide member that supports a sheet being conveyed, a reflective photoelectric detector embedded in the surface of the guide member, and a reflectance of the surface facing the guide member that is equal to the reflectance of the sheet. 1. A sheet detection device comprising: a light shielding member disposed opposite to the photoelectric detector and set to a significantly lower value than the photoelectric detector. 2. A guide member that supports the sheet to be conveyed, a light shielding member disposed opposite to the guide member, and a light emitting element and a light receiving element embedded oppositely in opposing surfaces of the guide member and the light shielding member. 1. A sheet detection device comprising: a transmission type photoelectric detector having a transmissive type photoelectric detector;