Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-12-17
2002-09-17
Allen, Stephone (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S577000, C073S293000, C356S436000, C340S619000
Reexamination Certificate
active
06452202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring the level of a liquid in a tank adopted in a liquid electrophotographic printer and, more particularly, to an apparatus for measuring the level of a liquid in a tank adopted in a liquid electrophotographic printer so that an error in measuring the level of a liquid due to solidification of developer can be reduced.
2. Description of the Related Art
An apparatus for measuring the level of a liquid contained in a tank is adopted in a liquid electrophotographic printer such as a laser printer or a copier using developer to provide information about the amount of developer remaining in the tank. The liquid electrophotographic printer informs a user to add developer at an appropriate time by displaying a message requesting refilling of the developer using information on the amount of remaining developer provided by the liquid level measuring apparatus. Thus, by requesting a supply of developer appropriately by means of the liquid level measuring apparatus, an incomplete print process or interruption of a print task during printing due to a lack of developer can be avoided.
FIG. 1
shows the structure of a general liquid electrophotographic printer. Referring to the drawing, a printer using developer includes a plurality of rollers
11
,
12
and
13
, a photoreceptor web
14
, a reset unit
15
, four laser scanning units
16
, four development units
30
, a drying unit
18
, and a transfer unit
20
.
The reset unit
15
includes an exposure unit
15
a
for emitting light to the photoreceptor web
14
to remove an electrostatic latent image, and a charging unit
15
b
for charging the photoreceptor web
14
to a predetermined electric potential. Reference numeral
39
denotes a waste developer collection tank.
The four laser scanning units
16
scan information of yellow (Y), magenta (M), cyan (C) and black (B) colors. The four development units
30
supply developer of yellow (Y), magenta (M), cyan (C) and black (B) colors.
Each of the development units
30
includes a developer supply tank
32
for supplying developer to the photoreceptor web
14
and a development tank
31
for collecting developer falling from the photoreceptor web
14
. Each development tank
31
includes a development roller
36
, a brush roller
37
for removing developer adhering to the development roller
36
, a squeegee roller
34
for separating a liquid carrier component of the developer supplied to the photoreceptor web
14
which is not used for image formation, and a plate
35
for collecting the carrier component flowing along the outer circumferential surface of the squeegee roller
34
into the development tank
31
.
The developer supply tank
32
is provided with a liquid carrier component, norpar (N), which is a solvent, and toner which is a development substance, or highly concentrated developer from a developer supply portion
38
and is provided with the developer from the development tank
31
. The developer contained in the developer supply tank
32
is supplied between the development roller
36
and the photoreceptor web
14
by a pump P.
In the printing process of the liquid electrophotographic printer having the above structure, the laser scanning unit
16
scans light onto a predetermined area of the photoreceptor web
14
circulating past the reset unit
15
. An electrostatic latent image is formed on the photoreceptor web
14
by the scanned light and the electrostatic latent image is developed by developer supplied from the developer supply tank
32
of the development unit
30
. A color image is formed on the photoreceptor web
14
by the laser scanning units
16
for scanning light of different color information and the development units
30
for performing development with developer of a corresponding color. Most of the liquid carrier component that is not used for image development of the developer supplied to the photoreceptor web
14
from the development unit
30
during development is collected in the development tank
31
. As the photoreceptor web
14
continues to rotate, the color image formed on the photoreceptor web
14
with toner which is a development substance is first transferred to a transfer roller
21
rotating in engagement with the photoreceptor web
14
, after passing the drying unit
18
for absorbing and removing the liquid carrier component remaining on the photoreceptor web
14
. Subsequently, the image on the transfer roller
21
is transferred to a sheet of paper
23
by the rotation of the transfer roller
21
and the fixation roller
22
which rotate in engagement with each other interposing the paper
23
inserted therebetween and make the paper
23
proceed.
There is a conventional apparatus for measuring the level of developer contained in the developer supply tank
32
by detecting the change in the amount of transmitted or reflected light with respect to the developer supply tank
32
. The liquid level measuring apparatus includes a light source (not shown) for emitting light at the height corresponding to the level of liquid to be measured with respect to the developer supply tank
32
, and a photodetector (not shown) for detecting light which is transmitted or the reflected light in a direction which is the same as or opposite to the light projecting direction with respect to the developer supply tank
32
. The developer supply tank
32
is made of a material such as plastic in order to prevent easy breakage. However, most developer supply tanks made of plastic have a strong affinity to the developer. As a result, an error occurs in the measurement of the level of liquid due to developer adhering to an inner wall of the plastic developer supply tank without a change in the liquid level.
As another example of the liquid level measuring apparatus, a float (not
15
shown) installed in a tank and a sensor (not shown) for detecting the amount of the positional displacement of the float. For example, a permanent magnet is built-in the float and a Hall sensor responding to a magnetic force is adopted. In such a liquid level measuring apparatus, a movement path having a width slightly greater than the outer diameter of the float is vertically installed at the tank to minimize the rate of the positional displacement of the float in the horizontal direction with respect to a vertical movement path of the float. However, in this case, the width of the movement path of the float can be less than the outer diameter of the float due to the developer fixedly adhering to the tank so that an error can occur in measuring the level of liquid. Also, the float must be manufactured according to the specific gravity of the developer subject to the test, which is inconvenient.
Meanwhile, there is another method of measuring the level of liquid by installing two electrode plates (not shown) in a tank and detecting the change in electrostatic capacitance measured by the electrode plates corresponding to the change in the level of the developer. However, in this method, when the developer fixedly adheres to the electrode plate, an error can occur in measuring the level of liquid.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide an apparatus for measuring the level of liquid contained in a tank which can reduce fixing of developer to the position where the level of liquid is measured so that an error in measuring the level of liquid can be reduced.
Accordingly, to achieve the above objective, there is provided an apparatus for measuring the level of a liquid contained in a tank, which comprises a tank, at least one exhaust pipe including a transparent portion in at least a part thereof, having one end thereof installed to be connected to the tank and the other end, horizontally extended a predetermined length from the one end, connected to a set supply path and/or the tank so that liquid can be collected, said exhaust pipe being installed at a predetermined height vertically from a bottom surface of
Allen Stephone
Samsung Electronics Co,. Ltd.
Spears Eric
Sughrue & Mion, PLLC
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