Pick-Up Assembly - Canon 1000 Service Manual

3. OPERATION AND TIMING
B. Pick-Up Assembly
1. Detecting Paper Size
a. Outline
The size of paper in the cassette is checked by the paper width detecting VR and the paper length
sensor unit mounted to the rear of the cassette holder.
When the cassette is inserted into the cassette holder, the paper length sensor unit and the paper width
detecting VR are actuated by the bosses on the cassette, and the actuation is used to find out the width and
the length of the paper and ultimately to identify its size as one of the default sizes.
The CLC1000 identifies the size of paper with reference to width and length and, at the same time,
determines where to reverse the scanner and the range of laser exposure.
The bosses used to push the paper length sensor unit and the paper width detecting VR operate in
association with the width guide plate and the length guide plate inside the cassette, and adjusting these
guides to suit the paper will establish the positions of the bosses (Figure 3-603).
b. Detecting the Size of Paper
The paper length sensor unit consists of two
photointerrupters, and the combination of outputs
of these two sensors is used to determine the
length of paper.
On the other hand, the paper width detecting
VR is a variable resistor, and the resistance
generated by the VR is used to determine the
width of paper.
Figure 3-602 shows the relationship between
the paper width and the output of the VR. The
proportional relationship is stored in the RAM on
the DC controller PCB. You must enter the basic
settings if you have replaced the cassette, VR, or
DC controller PCB or if you have initialized the
RAM on the DC controller. (See chapter 7. II.
Standards and Adjustments G. 1. Registering the
Cassette/Multifeeder Paper Width Basic Setting.)
3-130
COPYRIGHT © 2001 CANON INC.
A4/A3
A4R
STMT-R
STMT-R
(139.7mm)
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
A4R A4
(210mm) (297mm)
Paper width
Figure 3-602