U.S. patent number 3,881,085 [Application Number 05/382,638] was granted by the patent office on 1975-04-29 for fuser control circuit for copying apparatus.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Robert L. Traister.
United States Patent |
3,881,085 |
Traister |
April 29, 1975 |
Fuser control circuit for copying apparatus
Abstract
A circuit for controlling power to the fuser of an electrostatic
type reproduction machine in response to voltage levels across the
fuser heat source as monitored by a transformer-rectifier
combination. The transformer signal output is applied to an R/C
circuit which controls a switching means in the fuser power line.
When a preset power level is reached, the switching means triggers
to interrupt power to the fuser heating source. A second R/C
control circuit serves, following a time interval, to reset the
switching means and resume power to the fuser heater.
Inventors: |
Traister; Robert L. (Webster,
NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
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Family
ID: |
26978442 |
Appl.
No.: |
05/382,638 |
Filed: |
July 29, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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312557 |
Dec 6, 1972 |
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Current U.S.
Class: |
219/216; 219/482;
219/499; 219/501; 399/336 |
Current CPC
Class: |
G03G
15/2003 (20130101); G05F 1/45 (20130101) |
Current International
Class: |
G03G
15/20 (20060101); G05F 1/45 (20060101); G05F
1/10 (20060101); H05b 001/00 () |
Field of
Search: |
;219/216,482,490,499,501,492,388 ;118/637 ;355/9 ;432/60 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Albritton; C. L.
Parent Case Text
This is a continuation, of application Ser. No. 312,557, filed Dec.
6, 1972, now abandoned.
Claims
What is claimed is:
1. In an apparatus for producing copies of documents having a fuser
for fixing images produced on the copies together with a heater for
heating the fuser, the combination of:
switching means to control power to said fuser heater adapted when
in a first switching state to provide power to said heater and when
in a second switching state to interrupt power to said heater;
and
control means for operating said switching means including
first capacitance means adapted on a predetermined charge to switch
said switching means to said second state whereby power to said
heater is interrupted,
means to charge said first capacitance means in proportion to line
voltages across said heater,
second capacitance means adapted on a predetermined charge to
switch said switching means to said first state and provide power
to said heater, and
means for charging said second capacitance means in response to
switching of said switching means to said second state.
2. In a reproduction apparatus for producing copies of original
documents, said apparatus including a fuser for permanently fixing
the images produced and a heater for heating said fuser, the
combination of:
switching means in the power circuit to said heater switchable on a
predetermined control signal to a blocking condition whereby power
to said heater is interrupted;
control switch means adapted in a first switch condition to provide
said control signal and in a second switch condition to terminate
said control signal; and
circuit means for operating said control switch means including
a first control capacitor,
means to charge said first capacitor in proportion to the power
supplied to said heater, said circuit means being adapted on a
predetermined first capacitor charge to trigger said control switch
means to said first switch condition whereby said switching means
is switched to a blocking condition and power to said heater is
interrupted, and
a second control capacitor chargeable upon switching of said
control switch means to said first switch condition, said circuit
means being adapted on a predetermined second capacitor charge to
trigger said control switch means to said second switch condition
whereby said switching means is switched to a conducting condition
and power is provided to said heater.
3. A power controller for the fuser of a copying machine adapted to
maintain a predetermined power input to the fuser despite
variations in line voltage, comprising, in combination:
means monitoring power input to said fuser adapted when said
predetermined power level is reached to cut off power to said
fuser; and
means adapted following a preset timed interval to restore power to
said fuser.
4. A power controller for the fuser of a copying machine adapted to
maintain a predetermined power input to the fuser despite
variations in line voltage, comprising, in combination:
means to cut off said fuser from the power source whenever power
input to said fuser exceeds a predetermined level; and
means to prevent restoration of power to said fuser for a preset
interval.
5. A power controller to protect the fuser of a copying machine
from excessive line voltage, comprising:
signal generating means for monitoring power levels across said
fuser adapted on a predetermined power level to generate a preset
control signal;
means responsive to said control signal to interrupt said line
voltage and terminate power to said fuser; and
timing means adapted following a timed interval to restore said
line voltage.
6. In an apparatus for producing copies of documents having a fuser
for fixing images produced on the copies together with a heater for
heating the fuser, the combination of:
switching means to control power to said fuser heater adapted when
in a first switching state to provide power to said heater and when
in a second switching state to interrupt power to said heater;
and
control means for operating said switching means including
means responding to power input to said heater adapted on a preset
power input to switch said switching means to said second state
whereby power to said heater is interrupted; and
means for switching said switch means to said first state following
a predetermined interval whereby to restore power to said fuser.
Description
This invention relates to a control for the fuser of electrostatic
type reproduction machines, and more particularly to a control
designed to provide a preset power input to the fuser heater
irrespective of changes in line voltage.
In electrostatic type reproduction machines, a toner delineated
image of the original document being copied is electrostatically
formed on the copy material. In order to render the image
permanent, the image is fused by passing copy material through a
heated oven, conventionally called a fuser. There, a combination of
heat and pressure melts, i.e., fuses, the toner onto the copy
material to form a permanent image.
In machines of this type, correct fuser temperatures are critical.
If the fuser temperature is too low, fusing may be incomplete. This
is most often evidenced by smearing or loss of image, particularly
when the copy material is handled. If the fuser temperature is too
high, there is danger that the copy material may burn or char.
Most fusers employ some type of electric heater, for example, a
quartz lamp, as a heat source. One obvious factor in the
performance of this type of fuser and in the operating temperatures
obtained by the fuser is line voltage. Where line voltages differ
from the optimum voltages for which the fuser heater is designed,
fuser temperatures may change which may result in improperly fused
copies.
It is a principal object of the present invention to provide a new
and improved fuser control.
It is a further object of the present invention to provide an
improved current level control for the fuser heat source of a
copying machine.
It is an object of the present invention to provide a circuit for
controlling line power to the heater of a copying machine fuser
designed to provide substantially constant power to the heater
irrespective of changes in line voltage.
It is an object of the present invention to provide an improved
fuser power controller effective to limit power input to the fuser
heater to that required for efficient fuser operation.
It is an object of the present invention to provide a power
controller for fusers permitting the fuser to be designed for
minimum anticipated line voltages with the assurance that line
voltages over and above the minimum line voltage will be
accomodated without adverse effect on the fuser or fuser
operation.
The invention relates to an apparatus for producing copies of
documents, comprising, in combination: a fuser for fixing images
produced on the copies; a heater for heating the fuser; switching
means to control power to the fuser heater adapted when in a first
switching state to provide power to the fuser heater and when in a
second switching state to interrupt power to the fuser heater; and
control means for operating the switching means including first
capacitance means effective on a predetermined charge to switch the
switching means to the second state whereby power to the heater is
interrupted, means to charge the first capacitance means in
proportion to line voltages across the heater, second capacitance
means effective on a predetermined charge to switch the switching
means to the first switching state and provide power to the heater,
and means for charging the second capacitance means in response to
switching of the switch means to the second switching state.
Other objects and advantages will be apparent from the following
description and drawings in which:
FIG. 1 is a schematic sectional view of an electrostatic type
reproduction machine embodying the principles of the present
invention;
FIG. 2 is an enlarged cross sectional view showing the fusing
apparatus of the reproduction machine shown in FIG. 1; and
FIG. 3 is a schematic circuit representation of the fuser control
arrangement of the present invention.
Referring particularly to FIGS. 1 and 2 of the drawings, an
exemplary copier/reproduction machine, designated generally by the
numeral 10 and incorporating the fuser control arrangement of the
present invention, is there shown. As in all electrostatic systems
such as the xerographic type machine illustrated, a light image of
a document to be reproduced is projected onto the sensitized
surface of a xerographic plate to form an electrostatic latent
image thereon. Thereafter, the latent image is developed with an
oppositely charged developing material to form a xerographic powder
or toner image, corresponding to the latent image on the plate
surface. The toner image is then electrostatically transferred to a
support surface where it is fused by a fusing device so that the
toner image is permanently adhered to the support surface.
In machine 10, an original document 12 to be copied is placed upon
a transparent support platen 14 fixedly arranged in an illumination
assembly generally indicated by the reference numeral 15 and
disposed at the left end of the machine. While upon the platen, the
document 12 is illuminated, thereby producing image rays
corresponding to the informational areas on the original. The image
rays are projected by means of an optical system onto the
photosensitive surface of a xerographic plate. In the exemplary
copier/reproduction machine 10, the xerographic plate is in the
form of a flexible photoconductive belt 17 supported in a belt
assembly 18.
The support assembly 18 for photoconductive belt 17 includes three
rollers 20, 21 and 22 located with parallel axes at approximately
the apices of a triangle. The upper roller 22 is rotatably
supported on shaft 23 which in turn is rotatably driven by a
suitable motor and drive means (not shown) to drive belt 17 in the
direction shown by the arrow in FIG. 1. During this movement of the
belt, the reflected light image of the original document 12 on
platen 14 is flashed upon the photoreceptor surface of belt 17 at
an exposure station 25 to produce an electrostatic latent image
thereon.
The continued movement of photoconductive belt 17 carries the
electrostatic image through a developing station 26 in which there
is positioned a developer assembly generally indicated by the
reference numeral 28. There the latent electrostatic image is
developed by means of toner through the use of a multiple magnetic
brush system 29.
The developed electrostatic image is carried by belt 17 to the
transfer station 30 where the developed image is transferred to a
support surface, normally a sheet of copy paper 31, brought forward
between transfer roller 32 and belt 17. In order to accomplish
transfer of the developed image solely by means of the electrical
bias on transfer roller 32, the copy sheet 31 is moved at
substantially the same speed as belt 17. A sheet transport
mechanism generally indicated at 34 is provided to advance copy
sheets 31 from a paper handling mechanism generally indicated by
the reference numeral 35 to transfer station 30.
Following transfer, the copy sheet 31 is stripped from belt 17 and
conveyed through fuser 38 wherein the toner image is permanently
fused or affixed thereto. Following fusing, the finished copy is
discharged into output tray 39.
Photoconductive belt 17 comprises a photoconductive layer of
selenium, which is the light receiving surface and imaging medium
for the apparatus, on a conductive backing. Further details
regarding the structure of the belt assembly 12 and its
relationship with the machine and support therefor may be found in
the copending application Ser. No. 102,312, filed Dec. 29, 1970,
and assigned to the same assignee, now U.S. Pat. No. 3,730,623,
issued May 1, 1973.
Referring now to FIG. 2, fuser 38 includes a suitable housing 40
within which is disposed a lower heated fuser roll 41 and an upper
pressure roll 42, rolls 41, 42 cooperating to form a nip through
which the copy sheets 31 pass. Rolls 41, 42 are suitably supported
for rotation and driven in unison by a suitable drive means (not
shown). Pressure roll 42 is comprised of a relatively soft material
such as Teflon, Neoprene, and the like with the result that
pressure contact between the rolls 41, 42 deforms the surface of
pressure roll 42. In this way, an increased contact arc between the
copy sheet and the heated fuser roll 41 is obtained.
In the exemplary arrangement illustrated, fuser roll 41 is hollow,
the roll 41 being formed from a suitable heat conductive material.
A source of heat such as lamp 44 is disposed therewithin. A
suitable temperature variable resistor, i.e., thermistor 45 is
supported on a fuser housing 40 in heat exchange relation therewith
to sense temperature conditions within the fuser housing 40.
Referring particularly to FIG. 3 of the drawing, a control circuit
50 is there shown schematically for controlling power input to
heating lamp 44 of fuser 40 irrespective of variations in line
voltage. Referring thereto, fuser heating lamp 44 is connected to a
source of power, shown here as line terminals L1, L2, by suitable
switching means, represented in exemplary fashion by silicon
controlled rectifier SCR 46.
A transformer 51 has primary winding 52 thereof tapped across
heating lamp 44. The secondary or output winding 53 of transformer
51 is connected to the input terminals of a suitable full wave
rectifier 55. A suitable source of d.c. bias or reference voltage,
represented by line 58, is provided, one terminal 56 of rectifier
55 being connected to voltage line 58. The other output terminal 57
of rectifier 55 is connected by line 64 to the control gate 65 of
switching amplifier 66 as will appear.
A control capacitor 60 is connected in parallel with terminals 56,
57 of rectifier 55 across lines 58, 64, a suitable capacitor
charging resistor 61 being provided in line 64 between rectifier
terminal 57 and capacitor 60. Discharge resistor 62 parallels
capacitor 60.
A suitable controller, such as switching amplifier 66, is provided
for controlling operation of SCR 46, the output terminal of
amplifier 66 being connected to the control terminal of SCR 46 by
line 69. Gate 67 of amplifier 60 is set to a suitable d.c.
reference voltage level from line 58, a suitable voltage
controlling resistor 63 being provided therein.
A capacitor 70 is connected through a suitable charging resistor 71
with line 69. Suitable voltage level resistors 74, 75 are connected
across amplifier 66 and between line 64 and ground respectively.
Discharge resistor 78 is provided between amplifier gate 67 and
ground, diode 79 providing a path from capacitor 70 to resistor
78.
During operation of copier 10, line voltages across heating lamp 44
of fuser 40 are constantly monitored by the control circuit
transformer 51. The output of winding 53 of transformer 51 is
rectified by rectifier 55, the resulting d.c. signal voltage
serving to charge control capacitor 60 through resistor 61.
When the charge on capacitor 60 reaches a predetermined level, the
signal voltage in line 64 to gate 65 of amplifier 66 switches
amplifier 66 to a conductive state. The resulting control signal in
line 69 triggers SCR 46 to a blocking condition thereby
interrupting power to fuser lamp 44.
It will be understood that with power to lamp 44 terminated, the
signal voltage generated by transformer 51 falls and control
capacitor 60 discharges through resistor 62.
With switching amplifier 66 conductive, the signal voltage in line
69 charges capacitor 70 through resistor 71. When the charge on
capacitor 70 reaches the predetermined level as determined by
resistors 74, 75, amplifier 66 is switched back to a non-conductive
state. With the loss of control signal in line 69, SCR 46 is reset
to a conductive state and power input to heating lamp 44 is
restored. As will be understood, capacitor 70, on switching of
amplifier 66 to a non-conductive state, will discharge through
resistor 78 in preparation for the next cycle.
While the invention has been described with reference to the
structure disclosed, it is not confined to the details set forth,
but is intended to cover such modifications or changes as may come
within the scope of the following claims.
* * * * *