Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1999-07-28
2001-08-07
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S109000
Reexamination Certificate
active
06270071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet supply device.
2. Description of the Related Art
A sheet supply device is used in image forming devices and other office equipment. As shown in FIGS.
1
(
a
) and
1
(
b
), a conventional sheet supply device includes a sheet supply roller
80
, an idle roller
82
, and a rotational shaft
84
, that all rotate around the same axis. The sheet supply roller
80
has a large radius portion
80
a
and a small radius portion
80
b.
The large radius portion
80
a
has a radius greater than the radius of the idle roller
82
. The small radius portion
80
b
has a radius smaller than the radius of the idle roller
82
. When the rotational shaft
84
is driven to rotate, the sheet supply roller
80
rotates along with the rotational shaft
84
. On the other hand, the idle roller
82
is freely rotatable around the rotational shaft
84
. A stack of sheets S are provided at a predetermined sheet supply position beneath the idle roller
82
. Although not shown in the drawings, an urging member is disposed at a side of the sheet S opposite from the idle roller
82
, and urges the sheet S toward the idle roller
82
.
When sheet supply operations are not being performed, the small radius portion
80
b
of the sheet supply roller
80
confronts the surface of the sheet S at the sheet supply position, and the idle roller
82
contacts the surface of the sheet S. In this way, the idle roller
82
maintains a minimum distance between the rotational shaft
84
and the sheet S.
When sheet supply operations are started, the rotational shaft
84
is driven to rotate in a direction indicated by an arrow B in FIG.
1
(
a
), and the sheet supply roller
80
rotates in association with the rotational shaft
84
. As a result, as shown in FIG.
1
(
a
) the large radius portion
80
a
of the sheet supply roller
80
comes into contact with the sheet S, and the idle roller
82
is separated from the sheet S. As the sheet supply roller
80
further rotates, the sheet S is fed toward the sheet feed rollers
86
,
88
because of friction between the sheet supply roller
80
and the sheet S. When the front edge of the sheet S reaches the sheet feed rollers
86
,
88
, the sheet feed rollers
86
,
88
pick up the sheet S and further transport the sheet S.
After the sheet S is picked up by the sheet feed rollers
86
,
88
, the small radius portion
80
b
again comes into confrontation with the sheet S. As a result, as shown in FIG,
1
(
b
), the idle roller
82
comes into contact with the sheet S, and the sheet supply roller
80
is separated from the sheet S. Then, the rotation of the sheet supply roller
80
is stopped. However, because the idle roller
82
is freely rotatable about the rotational shaft
84
, the idle roller
82
is rotated as the sheet S is fed by the sheet feed roller
86
,
88
because of friction generated between the idle roller
82
and the sheet S. Accordingly, the sheet S is smoothly transported without any undesirably large force being generated between the idle roller
82
and the sheet S.
Usually, the large radius portion
80
a
of the sheet supply roller
80
is formed from a soft material, such as rubber, that has a large friction coefficient. Therefore, when the sheet supply roller
80
is used for a long period of time, the outer peripheral surface of the large radius portion
80
a
is gradually worn down by friction. On the other hand, the idle roller
82
is normally formed from a material with a low friction coefficient, and that is much harder than the material of the sheet supply roller
80
. For this reason, the idle roller
82
wears down much slower than the sheet supply roller
80
. Accordingly, the difference between the radius of the large radius portion
80
a
and the radius of the idle roller
82
is gradually reduced with passage of time.
The relationship of the radius of the large radius portion
80
a
and the radius of the idle roller
82
with respect to the passage of time is shown in graphical form in FIG.
2
. After the sheet supply roller
80
has been operated for a cumulative operation time of t
1
, the difference between the radius of the large radius portion
80
a
and the idle roller
82
reaches a minimum tolerance value A. When the difference is reduced to lower than the minimum tolerance value A, sheets S will quite frequently be improperly picked up by the sheet supply roller
80
, thereby preventing proper sheet supply operations.
Therefore, the sheet supply roller
80
must be replaced with a new one before the cumulative operation time of the sheet supply roller
80
exceeds the value t
1
. However, the sheet supply roller
80
is expensive to replace, so it is desirable to increase the life of the sheet supply roller
80
.
SUMMARY OF THE INVENTION
It is an objective of the present invention to overcome the other described problems and also to provide a sheet supply device which has a sheet supply roller with a longer life.
In order to achieve the above and other objectives, there is provided a sheet supply device including a rotatable shaft, a sheet supply roller, and at least one idle roller. The sheet supply roller is fixed to the shaft such that the sheet supply roller rotates along with the shaft. The sheet supply roller supplies the recording sheet in a predetermined direction while rotating. The sheet supply roller has a cross-section formed of a large radius segmental portion and a small radius segmental portion. The idle roller is freely rotatably mounted around the shaft and has an inner surface to contact the shaft and an outer surface to contact the recording medium. The idle roller has a distance between the inner surface and the outer surface. At least one of the rotatable shaft and the inner surface of the idle roller is formed so that the inner surface of the idle roller is worn down to decrease the distance between the inner surface and the outer surface because of a friction generated between the shaft and the inner surface of the idle roller.
REFERENCES:
patent: 4905984 (1990-03-01), Haigh
patent: 5372359 (1994-12-01), Miura et al.
patent: 5437444 (1995-08-01), Kawakami et al.
patent: 5582399 (1996-12-01), Sugiura
patent: 5857671 (1999-01-01), Kato et al.
patent: 6070867 (2000-06-01), Tsurumi et al.
Brother Kogyo Kabushiki Kaisha
Oliff & Berridge PLC.
Skaggs H. Grant
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