Paper Jam Detection - Canon LBP-1000 Service Manual

CHAPTER 2
C. Paper Jam Detection
The following paper sensors are installed to detect whether the paper is present or not and
whether the paper is fed normally or not.
• Top-of-page sensor (PS502)
• Delivery sensor (PS503)
The CPU determines if a paper jam has occurred by checking for the presence of paper in the
sensor at the timing stored in the CPU.
If the CPU determines that a paper jam has occurred, it stops print operation and notifies the
jam to the video controller.
1. Pick-up delay jam
This printer performs retry control to redress the pick-up delay jam caused by pick-up error.
Pick-up operation is conducted a maximum of twice at the all pick-up sources.
If the top-of-page sensor (PS502) cannot detect the leading edge of the paper within a speci-
fied period of time (T) after the start of pick-up operation, the printer performs pick-up opera-
tion once again. The CPU assesses a pick-up delay jam, if PS502 cannot detect the leading edge
of the paper within the specified period of time (T) after the start of the 2nd pick-up operation.
The specified period of time (T) mentioned above is as follows.
• Paper pick-up from the multi-purpose tray: T= about 2.5 seconds
• Paper pick-up from the cassette: T= about 3.0 seconds
• Paper pick-up from the paper feeder: T= about 4.4 seconds
2. Pick-up stationary jam
a. When WAIT period starts
The CPU assesses a pick-up stationary jam if the top-of-page sensor detects paper when the
WAIT period starts.
b. During paper feeding
The CPU assesses a pick-up stationary jam if the top-of-page sensor (PS502) cannot detect the
trailing edge of the paper within 6.8 seconds after detecting the leading edge of the paper.
3. Delivery delay jam
The CPU assesses a delivery delay jam if the paper does not reach the delivery sensor (PS503)
within a specified period of time (T) after the top-of-page sensor (PS502) detects the leading edge
of the paper.
• Paper 246mm or more: T= about 4.8 seconds
• Paper 200mm to 246mm (246mm not inclusive): T= about 4.9 seconds
• Paper less than 200mm: T= about 9.9 seconds
4. Wrapping jam
The CPU assesses a wrapping jam if the delivery sensor (PS503) detects no paper in a period
from about 0.5 seconds after PS503 detects the leading edge of the paper until about 4.0 sec-
onds after the top-of-page sensor (PS502) detects the trailing edge of the paper.
5. Delivery stationary jam
a. When WAIT period starts
The CPU assesses a delivery stationary jam if the delivery sensor (PS503) detects paper when the
WAIT period starts.
b. During paper feeding
The CPU assesses a delivery stationary jam if the delivery sensor (PS503) cannot detect the trail-
ing edge of the paper within a specified period of time (T) after the top-of-page sensor (PS502)
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