Electricity: motive power systems – Positional servo systems – Analog computation
Reexamination Certificate
2000-12-19
2003-02-25
Donels, Jeffrey (Department: 2837)
Electricity: motive power systems
Positional servo systems
Analog computation
C318S015000
Reexamination Certificate
active
06525503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the drive mechanism for a scanner.
2. Background of the Invention
A scanner is a common computer peripheral equipment which uses an internal image pick-up device to pick up document images and to transfer the pick-up image into digital signals as input to a computer which then performs image processing of the document.
FIG. 1A
is a diagram showing a conventional scanner
1
. The conventional scanner
1
comprises a housing
12
with an upper opening
11
, a document
13
to be scanned, and an image pick-up device
14
. The document
13
can be placed above the upper opening
11
of the housing
12
, and the image pick-up device
14
scans the image by a drive mechanism (not shown) provided by the scanner
1
, with the image pick-up device
14
being an optical path device of Charged Couple Device (CCD) or Contact Image Sensor (CIS).
FIG. 1B
illustrates the drive mechanism
2
of the conventional scanner
1
. The drive mechanism
2
is mounted in the housing
12
and positioned below the document
13
, and comprises a scanning path
21
, a delivery device
22
, and a set of decelerated gears and a motor
24
.
The scanning path
21
consists of a slip bar
211
and a sliding rail
212
, with the slip bar
211
and the sliding rail
212
parallel each other, and with the image pick-up device
14
having a guide hole
141
and rotating wheel
142
that cooperate with slip bar
211
and sliding rail
212
, respectively, so as to scan back and forth in the scan path
21
.
The delivery device
22
comprises an actuating gear
221
, a passive gear
222
and an annular gear belt
223
, with the actuating gear
221
and the passive gear
222
mounted in the two ends of the housing
12
respectively, the annular gear belt
223
being set on the two gears
221
,
222
respectively and parallel with scan path
21
, and with the annular gear belt
223
combining with the image pick-up device
14
.
A reduction gear set
23
is combined with the motor
24
and the actuating gear
221
, and its primary function is to provide appropriate reduction ratio so that rotational speed (torque) of the motor
24
is reduced to an appropriate extent and then to communicate motive power to the actuating gear
221
.
Thus the scanning mode of the drive mechanism
2
is to promote the rotation of the delivery device
22
by way of output power of the motor
24
so that the annular gear belt
223
drives the image pick-up device
14
to move back and forth in the scan path
21
so as to scan the document
13
.
However there are many design problems with the conventional scanner
1
. Since current consumers not only demand to increase the resolution of the scanner
1
, they also demand that scanning speed be as fast as possible. However, if the resolution of the scanner
1
is increased, the speed of image processing becomes slow, which then requires adjusting the reduction ratio of the reduction gear set
23
or adopting higher rotational speed of the motor
24
so as to increase the scanning speed of the scanner
1
.
Unfortunately, all motors, whether DC motor or stepping motor, have defined specifications and rotational speed (torque) range limits, so little can be done to increase the rotational speed of the motor
24
. Hence increase in the speed of image processing is typically achieved by changing the reduction ratio of the reduction gear set
23
. However, even changing the reduction ratio of the reduction gear set
23
may not be enough.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a drive mechanism for a scanner. The drive mechanism provides wider scope of scanning speed for a scanner and is matched with the scanning speed design of the scanner that has various resolutions.
The drive mechanism according to the present invention comprises a delivery device, two passive skew gears, a first rotational speed motor and a second rotational speed motor. The delivery device consists of an actuating wheel, a passive wheel and an annular conveyor belt, with the conveyor belt carried by the actuating wheel and the passive wheel. The axes of the two passive skew gears are attached to two ends of the inside diameter of the actuating wheel. The output shaft of the first rotational speed motor is provided with an actuating skew gear that engages the two passive skew gears. The output shaft of the second rotational speed motor is provided with an actuating skew gear that engages the two passive skew gears. The drive mechanism uses the two motors to drive the two passive skew gears so as to better control the rotational speed and to scan the document image.
The two passive skew gears and two actuating wheels of two motors form a differential gear. Because the axes of two passive skew gears are attached to two ends of the inside diameter of the actuating wheel, averaging the sum of the first motor rotational speed and the second motor rotational speed will provide the rotational speed of the actuating wheel. Hence the motors of two different rotational speeds are used to mutually coordinate and obtain a particular or more appropriate rotational speed value for the actuating wheel.
REFERENCES:
patent: 3586259 (1971-06-01), Richt
patent: 5737216 (1998-04-01), Hokari
patent: 6134978 (2000-10-01), Lin
Donels Jeffrey
Umax Data Systems Inc.
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