Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-10-24
2001-12-04
Wu, Daniel J. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S644000, C340S653000, C361S160000, C361S206000
Reexamination Certificate
active
06326898
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an image forming system, and more particularly relates to a system and method for determining the operability of a solenoid used in the image forming system.
BACKGROUND OF THE INVENTION
Today, electrophotographic printing systems, such as digital copiers, are widely used in many business and commercial environments. In a digital copier, an image of a document is captured by an input scanning facility, and converted into selected digital image data. This image data is then typically compressed by a control unit, then either forwarded to a suitable printing module or stored in system memory.
In general these image forming systems contain a plurality of solenoids. The solenoids perform many different functions within the image forming system. In order to improve the quality and reliability of manufactured machines, the health of the various components that constitute the machines is important. The most common failure mode of a solenoid is that it does not pull-in all the way or drop-out all the way in a specified amount of time.
One common technique for measuring solenoid health is by computing the time required for the solenoid plunger to pull-in from an initial position of extension, or drop-out from an initial position of retraction. If the solenoid plunger moves in an amount of time equal to a predetermined “pull-in” time, or “drop-out” time, then the solenoid is deemed to be functioning properly. This time measurement technique assumes two things: the solenoid plunger actually began at the full out position, and the solenoid plunger actually ended at the full-in position, or vice-versa.
Experience, however, has shown that an improperly functioning solenoid can appear to be functioning properly if solely judged by the pull-in time. For example, in situations where a solenoid fails to drop-out completely because the frictional force between the plunger and solenoid barrel is too great for the return spring to overcome, the measured pull-in time may still meet specification. This is because the plunger, which is not actually pulling in the full and complete stroke, is moving a less than complete distance in the predetermined amount of time according to specification. The converse may also occur. For example, in situations where a solenoid may not always pull completely in because it cannot overcome an external load and/or internal friction forces, the drop-out may appear to be normal because movement occurred in the predetermined amount of time according to specification, although the solenoid did not drop-out the full and complete stroke.
Experience has also shown that an improperly functioning solenoid can also appear to be operating properly if solely judged by current values in particular regions of a current waveform. To further clarify, when an improperly functioning solenoid moves from a fully extended position to a fully retracted position, or vice versa, in an inordinate, or excessive, amount of time, the measured current values may still appear correct with regard to solenoid position, even though the solenoid is actually malfunctioning.
SUMMARY OF THE INVENTION
For the foregoing reasons, there exists in the art a need for a system and method for determining if a solenoid is functioning properly by considering whether the solenoid plunger fails to move completely between a fully extended and fully retracted position in a predetermined time period. The present invention is directed toward further solutions in this art.
The present invention provides a method for diagnosing whether a solenoid is functioning properly in an image forming system by providing an actuating voltage with an associated value to activate a solenoid. A corresponding actuating current is measured, along with a time value, at an initial stage. A plunger of the solenoid moves between a first position and a second position. Based at least partially on the measured actuating current before and after plunger movement, and time values at the beginning and ending points of the plunger movement, a determination can be made as to whether the solenoid is functioning properly.
According to another aspect, the measured time and actuating current values are compared with predetermined time and actuating current values for plunger movement initiation, and plunger movement cessation, which correspond to a properly functioning solenoid. The differences between the measured actuating current and time values and the predetermined actuating current and time values are calculated, and the differences serve as an indication as to whether the solenoid is functioning properly based at least partially on whether the differences are within or outside a predetermined range.
According to still another aspect, the determining step includes evaluating the measured actuating current and time values relative to predetermined actuating current and time values for properly functioning solenoids. The measured actuating current and time values are then compared with predetermined actuating current and time values, such that if there is a substantial match within a predetermined margin of error or range, then the solenoid is considered to be properly functioning.
According to still another aspect, the predetermined actuating current and time values can be determined by either empirical or formulaic procedures.
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O'Leyar Stephen C.
Siegel Robert P.
Lahive & Cockfield LLP
Pham Toan
Wu Daniel J.
Xerox Corporation
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