Electrophotography – Image formation – Fixing
Reexamination Certificate
1999-10-14
2001-09-18
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Fixing
Reexamination Certificate
active
06292646
ABSTRACT:
BACKGROUND OF THE INVENTION
Silicone oil supply webs are known which provide a release agent to a fuser in an electrophotographic process such as that used in electrophotographic printers. Such printers produce hardcopy images on paper or other print media through precise deposition of toner onto the paper. The toner is adhered to the paper by a fuser hot roller, which heats and melts the toner to fuse it to the paper. As the toner melts, it becomes tacky and has a tendency to adhere to the fuser hot roller. Over time, accumulated toner can compromise the print process. Application of a lubricating substance such as silicone oil to the fuser hot roller serves to prevent adhesion of the toner, and also smooths the toner surface on the paper. An oil supply web provides a controlled supply of silicone oil to a fuser hot roller during the print process.
Referring to prior art
FIG. 1
, an oil supply web
10
is a sheet of fibrous or membrane material held against the fuser hot roller
18
by an idling bias roller
20
. The web is wrapped around a supply roller
12
and a take-up roller
14
. Oil delivery is controlled by indexing the take-up and supply rollers
14
,
12
as the web is held against the fuser hot roller by the bias roller
20
. As the web
10
is fed in a direction opposite to the rotation of the fuser hot roller, abrasive and frictional forces clean the fuser hot roller
18
. Since the fuser hot roller
18
rotates in a direction opposite to the web
10
, the web remains taut between the idling bias roller
20
and the take-up roller
14
. Concurrently, silicone oil absorbed or embedded in the web is applied onto the fuser hot roller upon contact therewith as the paper
22
advances. A controlled supply of oil is therefore provided to the fuser hot roller as the web advances from the supply roller
12
to the take-up roller
14
.
The oil supply web
10
, however, can become unraveled when the fuser hot roller is rotated in a reverse direction. Reverse rotation can result from attempts
1
o clear paper jams. Referring to prior art
FIG. 2
, reverse rotation can occur from a user removing paper
24
in the direction of arrow
26
, or from rotation of a jam-clearing knob
28
. Frictional contact between the web and the fuser hot roller due to the idling bias roller
20
occurs as the fuser hot roller
18
rotates in the reverse direction. Such reverse rotation causes the web
10
to unravel from the supply roller
12
into the jam zone
30
. Unraveling of the web causes the web material to jam, decreases the web supply lifetime, and can also cause further problems if excess oil leaks onto other parts.
It would be beneficial, therefore, to provide an apparatus which prevents the oil supply web from unraveling when the fuser hot roller is rotated in a reverse direction, yet which does not hinder the rotation of the fuser hot roller in the normal direction, so as to allow both normal or jam-clearing hot roller rotation without compromising the oil supply web.
BRIEF SUMMARY OF THE INVENTION
An apparatus and method are provided for preventing unraveling of an oil supply web by the selective application of a locking mechanism to a web supply roller when a fuser hot roller or other fuser drive roller is forced to rotate in a reverse rotation. The locking mechanism is released when the fuser hot roller resumes normal rotation.
A pawl arm is adapted for pivotal movement into locking engagement with the web supply roller. A braking element, such as a ratchet latch attached to the end of the pawl arm, contacts a rotary follower connected to the web supply roller. The braking element is disengaged when the fuser hot roller resumes rotation in the normal direction, as the pawl arm is pivoted out of engagement with the rotary follower. In this manner, the web operates to lubricate and condition the fuser hot roller from controlled rotation of the web supply roller when the fuser hot roller is rotating in the normal direction, and is prevented from unraveling when the fuser hot roller is rotated in a reverse direction.
Selective rotational communication between the fuser hot roller and the pawl arm transfers rotational force to the pawl arm when the fuser hot roller changes direction. Rotational communication is maintained until the pawl reaches a predetermined point of engagement or disengagement with the web supply roller, depending on whether the fuser hot roller is rotating in the normal or reverse direction, respectively. When the pawl arm has reached such a predetermined point, slippable communication between the fuser hot roller and the pawl arm is resumed to maintain a slight drag on the pawl so as to maintain the position of the pawl in the engaged or disengaged position.
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patent: 5156350 (1992-10-01), Wales et al.
patent: 5293202 (1994-03-01), Adachi et al.
patent: 5344089 (1994-09-01), Crowley et al.
patent: 5472153 (1995-12-01), Crowley et al.
patent: 5505401 (1996-04-01), Lamothe
patent: 5530528 (1996-06-01), Houki et al.
patent: 5617134 (1997-04-01), Lamothe
patent: 5651511 (1997-07-01), Crowley et al.
patent: 5768675 (1998-06-01), Estabrooks
patent: 5848341 (1998-12-01), Watanabe
patent: 6006063 (1999-12-01), Shimizu et al.
Maul Michael David
Rush Edward Alan
Lexmark International Inc.
Royer William J.
Sanderson Michael T.
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