Electrophotography – Machine operation – Electrical connection
Reexamination Certificate
2000-03-07
2001-08-14
Beatty, Robert (Department: 2852)
Electrophotography
Machine operation
Electrical connection
C399S330000, C439S242000
Reexamination Certificate
active
06275669
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fixing device that heats and melts toner adhering to paper in order to fix the toner thereto and form an image.
2. Description of the Related Art
In a conventional thermal fixing device of a laser beam printer, a hollow cylindrical drum, made of aluminum and covered by heat-resistant rubber, is used as a fixing drum, and a halogen heater is disposed inside the drum to heat the fixing drum.
The halogen heater is provided with a supporting member and a power feeding member, separately. The halogen heater is supported on the frame using the supporting member, while electric power is supplied to the halogen heater using the power feeding member through a flexible lead wire extending from the halogen heater. In the fixing device structured as described above, a power feeding member and a heater supporting member must be provided and assembled. Accordingly, the number of components as well as the number of assembling steps are increased and productivity is reduced. Another problem is that the halogen heater is pressed against the frame and secured directly thereto, which may cause the halogen heater to break.
To address the forgoing problems, Japanese Laid-Open Patent Publication No. 8-44233 discloses a fixing device in which a heater, which has, at its opposite ends, high rigidity pin-shaped terminals, is used to allow support of the heater as well as power supply to the heater. In such a heater, if the terminals at the opposite ends are supported while power is supplied thereto, a heater tube can be supported and supplied with power at the same time.
FIG. 12
shows the heater disclosed in the above publication. As shown in
FIG. 12
, a power feeding member of the heater is a thin metal plate
101
, bent into a U-shape, that holds a terminal
104
of a heater tube
103
disposed along a central axis of a fixing roller
102
. A power feeding terminal
105
is laminated with the thin metal plate
101
, and the power feeding terminal
105
and the thin metal plate
101
are secured to the frame
107
by a screw
106
.
The halogen heater heats up to high temperatures quickly when supplied with electric power. Quartz glass surrounding the periphery of the halogen heater has a lower linear thermal expansion coefficient than usual alkaline line glass, and a high stability against drastic temperature changes. However, quartz glass is low in mechanical strength and susceptible to mechanical shock and strain. Therefore, when the terminal
104
of the halogen heater is directly secured to the power feeding terminal
105
of the frame
107
, as disclosed in the above publication, the heater is apt to be broken due to mechanical strain caused by the difference in thermal expansion coefficient between the heater and the frame.
In another fixing device, a terminal of a heater is held by a power feeding terminal urged by a spring. In this case, the spring urging force is changed due to the difference in thermal expansion coefficient between the heater and the frame, and electric contact becomes unstable.
In still another fixing device, contact surfaces of a terminal of a heater and a terminal supporting member are made smooth, and the terminal is screw-held to the supporting member slidably under a predetermined pressure. However, polishing and smoothing is difficult. In addition, the terminal of the heater is usually made of tungsten, while the terminal supporting member, that is, an electrode, is made of phosphor bronze based upon this material's resilience and conductivity. The difference in hardness of the metals might cause biting and make sliding impossible.
SUMMARY OF THE INVENTION
An object of the invention, therefore, is to solve the forgoing problems and to provide a cost-effective power feeding member capable of stably supporting a heater tube without causing a breakage and stably supplying electric power to the heater tube.
In a fixing device according to the invention, an electrode of the power feeding member is supported by a supporting member such that the electrode can shift. Accordingly, even when the heater thermally expands, the electrode shifts in correspondence with the expansion. Thus, there is substantially no chance that the heater will break. Further, since terminals of the heater are firmly secured to respective electrodes, the heater can be stably supported by the electrodes and, at the same time, electric power can be stably supplied to the heater without causing poor electric contact. Since the supporting member also serves as the power feeding member, the number of components as well as the number of assembling steps can be reduced, resulting in a reduction of manufacturing cost and an increase of productivity.
According to the invention, the supporting member absorbs mechanical strain caused by the difference in thermal expansion coefficient between the heater and a frame, and thus the heater is reliably prevented from being broken.
In order to absorb mechanical strain, the supporting member is made of a resilient material that can resiliently deform and shift. Such resilience allows the heater to be stably supported at a predetermined position.
Further, the supporting member may be made of a resiliently deformable conductive material and integrally formed with the electrode. When the supporting member is integrally formed with the electrode, one member can serve as a heater supporting member and a power feeding member as well as an electrode supporting member. Accordingly, the number of components and the number of assembling steps are reduced, resulting in a reduction of manufacturing cost and an increase of productivity.
In addition, when the supporting member that supports the electrode is formed by a portion of the frame, the number of components and the number of assembling steps are reduced, resulting in a reduction of manufacturing cost and an increase of productivity.
When a halogen heater using a quartz glass tube is used as the heater, the heater can be stably supported without a breakage, even under generation of a great amount of heat or a quick rise in temperature and, as a result, performance of the fixing device is increased. No breakage occurs because quartz glass has a low linear thermal expansion coefficient and high stability against drastic temperature changes.
When pin-shaped terminals having rigidity capable of supporting the heater are used as the terminals, the heater can be supported stably only by the terminals and no other heater supporting members are required, which contributes to a reduction of manufacturing cost of the printer.
Only one of the terminals of the heater may be arranged to be held by a shiftable electrode, while an electrode for the other terminal is simple in structure. Compared with a heater supported at its both ends by shiftable electrodes, the number of components and the number of assembling steps are reduced, resulting in a reduction of manufacturing cost and an increase of productivity.
REFERENCES:
patent: 5974285 (1999-10-01), Tomatsu
patent: 8-44233 (1966-02-01), None
Beatty Robert
Brother Kogyo Kabushiki Kaisha
Oliff & Berridg,e PLC
LandOfFree
Thermal fixing device having electric heater connection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal fixing device having electric heater connection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal fixing device having electric heater connection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2461022