Automatic overhead transparency detection

The printer enters overhead transparency (OHT) mode when the user selects to print on transparencies through the printer driver or by selecting OHT as the media type at the printer control panel. The OHT sensors (PS1801 and PS1802, see figure 57 on page 184) are installed in front of the registration roller to detect transparencies even if the user has not set the media type at the printer control panel. The controller board monitors these sensors to execute OHT detection.

PS1801 and PS1802 consist of light emission and light reception units. When a transparency is used, the light emitted from the light emitter unit goes through the transparency and is received by the light receptor. As a result, the controller board determines that the fed media is a transparency and enters the OHT mode.

Paper pick-up begins when the print signal is sent. The pick-up roller is lowered to the paper level, and the main motor (M4) rotates the roller. This process feeds the paper into the printer from the input trays.

• Tray pick-up — When the pick-up motor is in normal rotation, the tray 2 pick-up roller, feed roller 1, and separation roller are driven. The paper is then picked up from the tray 2 pick-up roller. In the case of reverse rotation, the tray 3 pick-up roller, feed roller 1, and separation roller are driven. The paper is then picked up from the tray 3 pick-up roller.

• Multi-feed prevention mechanism — During paper pick-up from tray 2 or 3, the separation roller prevents multi-feeding.

• Tray 2 last page detection — The last-page sensor (PS29) consists of a light emitter and light receiver. When paper is present in tray 2, the light from the light emitter is reflected by the paper and received by the light receiver. However, when the last page is picked up, the light from the light emitter is transmitted inside the printer and does not reach the light receiver. The controller board signals the formatter that there is no paper in tray 2 and stops formation of the next image. The tray 2 last-page detection prevents the imaging drum and the transfer drum from getting dirty by detecting that no paper is available before the next image is written.

Figure 55. Tray 2 and 3 pick-up

1

Pick-up motor drive signal

M4

Main motor

2

Feed roller clutch drive signal

M5

Pick-up motor

3

Tray pick-up solenoid drive signal

SL3

Tray pick-up solenoid

4

Registration roller clutch drive signal

CL1

Registration roller clutch

5

Main motor drive signal

CL2

Feed roller clutch

• Tray 1 pick-up — One sheet of paper is pressed to the multipurpose pick-up roller by the paper lifting plate and is picked up by the rotation of the pick-up roller. Any extra sheets are removed by the separation pad, then sent into the printer. Operation after transmission is the same as for tray pick-up except that the paper lifting plate solenoid is reset on to lower the paper lifting plate right after registration roller rotation.

• Tray 1 paper-width sensor — The tray 1 paper-width sensor (PS1701) detects the paper width when the user adjusts the media width guides, which moves the slide resistance connected with the size-control plate. When paper is loaded in tray 1, the controller board detects the paper width. If the paper width is not the width specified by the formatter, the controller board notifies a paper-size failure to the formatter and stops the printer.

• Tray 1 last-page detection — The tray 1 last-page sensor (PS19) monitors the rotation of the last-page detection roller in tray 1 and detects the last page. If the tray has two or more pages, the last page detection roller does not rotate at pick-up. When the last page is picked up, the last-page detection roller rotates past the page and PS19 and sends an off to signal the controller board. The controller board then signals the formatter that no pages are in tray 1 and stops the next image formation. The PS19 detects no page before the next image is written and prevents the imaging drum and the transfer drum from getting dirty.

Laserjet P2015 Stop Motor

1

Registration roller clutch drive signal

SL4

Lifting plate solenoid

2

Main motor drive signal

CL1

Registration roller clutch

3

Registration roller paper detection

CL3

Tray 1 pick-up clutch

signal

PS1

Registration roller paper

4

Tray 1 pick-up clutch drive signal

sensor

5

Tray 1 paper detection signal

PS19

Tray 1 last page sensor

6

Lifting plate position detection signal

PS1301

Tray 1 page sensor

7

Lifting plate solenoid drive signal

PS1302

Lifting plate position sensor

8

Tray 1 last paper detection signal

PS1701

Tray 1 paper width sensor

9

Tray 1 paper width detection signal

PS1801

OHT sensor 1

10

OHT detection signal

PS1802

OHT sensor 2

11

OHT detection signal

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