Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-11-26
2002-08-27
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S276000, C029S895230, C029S895320
Reexamination Certificate
active
06440347
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is, for example, for an image forming apparatus employing an image forming process such as electrophotographic technique or electrostatic recording technique, and relates to a method of manufacturing a tube-covered roller for use in a heat fixing device which, for a fixed image, carries out a heat fixing treatment of an unfixed toner image of image information formed and born on a recording member (including a transfer member, a print paper sheet, a light-sensitive paper sheet and an electrostatic recording paper sheet) according to a transfer mode or a direct mode in an image forming process portion.
2. Description of Related Art
As a fixing device included in an image forming apparatus employing electrophotographic technique or electrostatic recording technique, there has widely been used a so-called heating roller type heat fixing device which fixes an unfixed toner image, as a permanent image, on a recording member by causing the recording member, which bears the unfixed toner image thereon, to pass through a nip portion formed by a fixing roller (heating roller) and a pressure roller which are rotated in a state of coming into pressed contact with each other.
In addition, as a heat fixing type system which does not supply electric power to a heat fixing device, particularly, at the time of standby, to reduce the power consumption to the utmost, a film heating type heat fixing device designed to fix a toner image on a recording member through a thin film between a fixing roller and a pressure roller has been disclosed, for example, in Japanese Laid-Open Patent Application No. Sho 63-313182, Japanese Laid-Open Patent Application No. Hei 2-157878, Japanese Laid-Open Patent Application No. Hei 4-44075, Japanese Laid-Open Patent Application No. Hei 4-204980, etc.
In such a heat fixing device, in order that a toner image can be fixed on a recording member without offset, a release-characteristics layer, such as a polytetrafluoroethylene (PTFE) or a perfluoroalkoxy tetrafluoroethylene copolymerizate (PFA), which shows a high ability in release characteristics, is formed on the uppermost layers of the fixing roller, the film and the pressure roller.
The release-characteristics layer is formed into a tube-like configuration, or is formed by an electrostatic spray, a dipping coating, or the like.
In addition, for the purpose of preventing the offset occurring when the surface of a fixing roller is charged up due to the conveyance of a recording member, the release-characteristics layer is sometimes doped with a conductive material such as a carbon black.
Alternatively, for example, employed is a pressure roller of the type in which a surface of the pressure roller is coated with a mixture of a fluoro rubber and fluoro-resin (fluoroplastic), such as Daiel-Latex GLS-213 (trade name, produced by Daikin Industries Ltd).
In particular, in order to satisfy a high durability and a high release stability according to the speedup of an image forming apparatus, a pressure roller covered with a tube has been employed frequently in recent years.
FIG. 6
is an illustration of a model of an example of the aforesaid pressure roller with a layer construction. A pressure roller
40
is made to have a tube-like configuration in such a manner that a sponge elastic layer
42
formed by forming a silicone rubber or a fluoro rubber, or by foaming a silicone rubber is formed on the exterior of a core
41
and a release-characteristics layer
43
made of a PTFE, a PFA, an FEP or the like is additionally formed on the sponge elastic layer
42
.
As a method of manufacturing the aforesaid pressure roller
40
, there has been known a method in which a core made of a metal such as aluminum is placed upright in the interior of a cylindrical mold so that a liquid silicone rubber is injected into the gap between the core and the mold to be vulcanized for curing, or a predetermined quantity of liquid silicone rubber is first injected into a blind-end cylindrical mold and a core is inserted into the mold so that the liquid silicone rubber rises in the gap between the core and the mold to cause the gap therebetween to be filled with the liquid silicone rubber, and then vulcanized for curing, and a surface of the cured silicone rubber is covered with a tube made of a fluororesin such as a PFA, a PTFE or the like and serving as the aforesaid release-characteristics layer.
However, the following problem will arise with the above-described manufacturing method as will be described hereinbelow.
The work of covering a pressure roller released from the mold with a fluororesin-made tube is difficult, so that there is a possibility that distortion occurs on the tube formed as the surface of the pressure roller or the tube is damaged.
For this reason, a method of accomplishing the formation of the silicone rubber and the coating of the fluororesin-made tube concurrently has taken place as disclosed in Japanese Laid-Open Patent Application No. Sho 50-7097, Japanese Laid-Open Patent Application No. Sho 51-27276, Japanese Laid-Open Patent Application No. Sho 61-169863, etc.
That is, as shown in
FIG. 7
, molds
52
a
and
52
b
constituting upper and lower end portions are fitted in a cylindrical mold
51
, and the end portion mold
52
a
has an opening
53
for injection of a liquid silicone rubber. In manufacturing a pressure roller, a core
41
made of aluminum or the like and a fluororesin tube
43
coated with a primer after etching of its inner surface are successively mounted in and on the end portion mold
52
a
, and the end portion mold
52
a
equipped with the core
41
and the fluororesin tube
43
is fitted in one end of the cylindrical mold
51
. Following this, the end portion mold
52
b
is fitted in an opening portion of the other end of the cylindrical mold
51
, and a liquid silicone rubber
42
is injected under a high pressure through an injection opening
53
of the end portion mold
52
a
into the gap between the core
41
and the fluororesin tube
43
so that the gap therebetween is filled with the liquid silicone rubber
42
. This filling pressure causes the expansion of the fluororesin tube
43
for the close attachment thereof to the inner circumferential surface of the cylindrical mold
51
, so that the fluororesin tube
43
is integrated with the silicone rubber material
42
.
Alternatively, a porous elastic material or member (silicone sponge) obtained by foaming a silicone rubber is shaped on a core and polished or ground up to a dimension of a predetermined outer diameter, while a non-shrinkable fluororesin tube having a diameter smaller than the outer diameter of the elastic material is expanded in a pressure-reducing container and the polished roller is inserted into the expanded tube. After the completion of the insertion thereinto, the assembly is again put under a normal pressure or the atmospheric pressure, so that the fluororesin tube is closely attached to an outer surface of the sponge elastic layer.
The above-described method has been employed for the fabrication of the pressure roller included in the heat fixing device.
However, the above-described pressure roller manufacturing method creates the following problems.
That is, at the setting of the fluororesin tube in the cylindrical mold or at the handling during the manufacturing process, it is considerably difficult that the pressure roller manufacturing worker performs operations without touching the surface of the fluororesin, so that there is a possibility of damages to the tube.
In addition, since the inner surface of the cylindrical mold directly comes into contact with the surface of the pressure roller at the formation, there is a possibility that the scratches or attached matters on the inner surface of the cylindrical mold are transferred directly onto the surface of the pressure roller.
Because of the above-mentioned problems, the release ability of the surface of the fluororesin layer of the pressure roller sometimes drops. In this case, when a toner
Goto Masahiro
Izawa Satoru
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