Electrophotography – Diagnostics – Component present or mounted
Reexamination Certificate
2002-12-16
2004-02-24
Grainger, Quana M. (Department: 2852)
Electrophotography
Diagnostics
Component present or mounted
C399S320000
Reexamination Certificate
active
06697579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as a copier or a printer, and more particularly pertains to a fixing unit for use in such an image forming apparatus for fixing a toner image onto a copy sheet. The fixing apparatus incorporates a heating roller or heat roller for fusing a toner image on the copy sheet and a pressing or pressure roller which is rendered in pressing contact with the heating roller to form a nip through which the copy sheet is transported for image fixation. This invention also relates to such an image forming apparatus provided with the fixing unit.
2. Description of the Related Art
A heater-type fixing unit for use in an image forming apparatus such as a copier and a printer generally has a cylindrical heating roller heated to a certain temperature and a cylindrical pressing roller which is rendered in pressing contact with the heating roller to form a nip between the heating and pressing rollers. A toner image which has been transferred onto a copy sheet, is fused by the heating roller and fixed on the copy sheet while the copy sheet is passing through the nip defined by the heating roller and the pressing roller.
Generally, in the above-mentioned fixing unit, the pressing roller is composed of a resilient material and is pressed against the heating roller. Specifically, the nip is defined by the contact surface on the outer surface of the heating roller and the contact surface of the pressing roller which is in pressing contact with the heating roller. While a copy sheet bearing a toner image is transported through the nip defined by the heating roller and pressing roller which are rotating, the toner image is fixed on the copy sheet by the heat of the heating roller and the pressing force is exerted to the copy sheet by the pressing roller.
Once the fixing unit is initialized for operation, the pressing roller of resilient material is constantly in pressing-contact with the heating roller at the nip with the result that it is highly likely that the resilient property of the pressing roller is deteriorated as time lapses in the case where the fixing unit is left unused for a long term, because the pressing roller is always under stress.
In view of the above, it is often the case that the image forming apparatus equipped with the fixing unit of the above mentioned construction is shipped or delivered to a customer with the pressing roller being kept off or away from the heating roller, namely, in a released state where the pressing roller is released from the pressing-contact against the heating roller. The pressing-contact is released to prevent the pressing roller having a certain resilient property, from being deformed due to unnecessary application of external force during a time period e.g. from shipment to installment and initialization of the image forming apparatus for actual use. In such a condition, after purchasing the image forming apparatus, a user has to resume the fixing unit to a pressing-contact state by him/herself to render the image forming apparatus (fixing unit) to an operable state.
An arrangement is conventionally known in which the fixing unit is selectively brought to a pressing-contact state where the pressing roller is pressed against the heating roller and a released state where the pressing roller is kept away from the heating roller by the manipulation of a control lever associated with the fixing unit. However, even with provision of such a control lever, a user may forget to set the control lever to the pressing-contact state, or inadvertently attempt to activate the image forming apparatus without setting the fixing unit to the pressing-contact state. With such a user's inadvertent operation and/or negligence of resuming the fixing unit to the pressing-contact state, it is highly likely to occur a mal-function of the image forming apparatus.
For example, the heating roller may be overheated as the pressing roller is not in contact with the heating roller and the heat produced by a heater within the heating roller is not shared by the heating and pressing rollers so that the heat roller may be heated rapidly above an allowed level before thermo-control system reacts, resulting in damage of the heat roller in worst case. A copy sheet may be jammed in the gap between the heating and pressing rollers in disengaged state, thus leading to failure in discharging the sheet. The image forming apparatus may indicate that an error is occurring and stop its operation, in response to detection of mal-function of the apparatus, such as the over-heating of the heating roller or sheet delivery error.
In view of the above, there has been proposed a fixing unit
101
as shown in FIG.
8
.
The fixing unit
101
shown in
FIG. 8
incorporates a heating roller
103
and a pressing roller
102
. Control levers
105
are provided in the fixing unit
101
to selectively set the fixing unit
101
between a pressing-contact state and a released state. At the time of shipment or delivery, a strip member
104
as shown in
FIG. 8
is adhered by a manufacturer to each control lever
105
with a front surface of the strip bearing a message to indicate a user the necessity of setting the lever to the pressing contact position. The message indicates a user that the control levers
105
should be manipulated in such a direction as to render the pressing roller
102
in pressing contact against the heating roller
103
before the user activates the image forming apparatus.
Specifically, each strip member
104
is adhesively attached to the front surface of the control lever
105
in such a manner that a user can notice the message on the front surface of the control lever
105
while the control lever
105
of the fixing unit
101
extends downward from the pressing roller
102
. The pressing roller
102
is kept off or away from the heating roller
103
when the control lever
105
extends downward and the annular portion
106
a
of a cam
106
engages the disk
107
which is provided on opposite ends of the heating roller
103
coaxially with but independently of the heating roller
103
. The cams
106
a
is provided on opposite ends of the pressing roller
102
coaxially with but independently of the pressing roller
102
. The strip member
104
bears, for example, a message on the front surface thereof to indicate the a user that the fixing unit
101
should be brought to a pressing-contact state by turning the control lever
105
upward before use, until the recessed portion
106
b
of the cam
106
comes into engagement with the disk
107
.
Although not illustrated in
FIG. 8
, the message may be any message as far as the message indicates or warns a user to use the apparatus under a requested condition, for example, “Lift the lever up before use!” The strip member or seal
104
is usually adhered to the free end of the control lever
105
sideway as shown in
FIG. 8
to facilitate removal of the strip
104
before initiation of the image forming apparatus.
However, there sometimes arises a case that a user may inadvertently remove the strip member
104
without reading the message thereon and attempt to activates the apparatus, leaving the control lever
105
at the initial downward extending state to keep the heating roller
103
away from the pressing roller
102
despite the fact that the message is displayed on the strip member
104
on the front surface of the control lever
105
, i.e., a site where the user can notice the message. Thus, the above idea of attaching the strip member
104
to urge the user to use the apparatus in a certain requested condition may fail because the user may forget to manipulate the control lever
105
according to the instruction on the strip member
104
, for instance. In such a case, as described above, an error indication may occur during activation of the apparatus, the heating roller may be damaged or broken due to the overheat when the apparatus is activated, or a copy sheet may be jammed.
Also, the conventional fixing devic
Ito Hiroshi
Tanabe Kenichi
Tomoe Tetsuro
Grainger Quana M.
Jordan and Hamburg LLP
Kyocera Mita Corporation
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