Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2000-05-10
2001-06-12
Pendegrass, Joan (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S113000
Reexamination Certificate
active
06246841
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a removable toner cartridge used in an image forming apparatus and, more particularly, to an arrangement for ascertaining the level of usable toner in a removable toner cartridge at any time throughout its use in a laser printer or an electrophotographic copier by determining the weight of the toner.
BACKGROUND OF THE INVENTION
A laser printer has a removable toner cartridge disposed therein for providing a supply of toner. The removable toner cartridge includes a photoconductive drum rotatably supported in a cleaner housing and a developer roll rotatably supported in a developer housing, which is slidably received in the cleaner housing. The developer roll transfers toner from the developer housing to the photoconductive drum when both are rotating to print a latent image on a recording medium.
Users of laser printers desire to know when the level of the usable toner in the removable toner cartridge is reaching the usable level at which quality printing will not occur. Various systems for sensing the amount of toner remaining in the removable toner cartridge have previously been suggested.
One sensing system has employed an optical sensor peering through a window defining a portion of a toner sump wall in the removable toner cartridge in which the toner is contained. When the optical sensor sees light through the sump window, a signal is produced to indicate to the user that the amount of remaining toner is low. However, this signal does not provide any indication of the level of the toner remaining in the removable toner cartridge but only that it is lower than a predetermined value. Because users print different quantities of sheets of a recording medium during a fixed period of time such as a day, for example, the indication of a low toner level might be satisfactory for a user printing a relatively large number of sheets of a recording medium but not satisfactory for a user printing a relatively small number of sheets of a recording medium during the same time period or vice versa.
Another sensing system has employed a torque sensing mechanism for sensing the torque driving a stirring paddle for the toner. When the torque required to stir the toner decreases below a minimum value, the torque sensing mechanism signals to the user of the laser printer that the level of the toner is low. The torque at any time during the cartridge life is related to the level of the remaining toner. Thus, this system is used to estimate the level of the remaining toner in the cartridge. However, this system is complex, relatively expensive, and can fail from a number of different causes.
Furthermore, in this torque sensing mechanism, the range of measurement is a relatively small percentage of the toner total load. Therefore, only about 30% of a full toner load is within the toner level measuring range of the torque sensing mechanism. Thus, the torque sensing mechanism does not enable measurement of substantially the entire range of the toner load.
U. S. Pat. No. 5,802,419 to Sakurai et al mentions various types of detecting mechanisms capable of detecting whether the amount of toner remaining in the removable toner cartridge is no more than a predetermined value. These include a mechanism employing a capacity detecting system, a mechanism employing a magnetic sensor, a light transmission type mechanism, and a mechanism that detects the weight of the toner. However, there is no discussion of how the weight of the remaining toner would be ascertained, and there is no suggestion that such mechanism is capable of determining the level of toner from detecting the weight of the toner. There also is no suggestion of using the detected weight of the toner to determine its level at any time.
SUMMARY OF THE INVENTION
The present invention determines the level of the toner through ascertaining the weight of the remaining toner in the removable toner cartridge at any time. This is accomplished by determining the magnitude of a reaction force, which is created by the developer housing of the removable toner cartridge including the amount of toner therein. The magnitude of the reaction force is converted to the weight of the toner in the developer housing of the removable toner cartridge.
The reaction force is measured by any low deflection force measurement device supported by the laser printer. The preferred low deflection force measurement device is a load cell.
The reaction force is transmitted from the developer housing through a single support surface on the developer housing engaging a roller, for example, connected to the load cell on the laser printer. The support surface is preferably a flat surface extending from the outer wall of the developer housing on one side thereof. It should be understood that the support surface also could be at the rear of the developer housing at a point between its sides if the laser printer had a different architecture.
Accordingly, since only one side of the developer housing is supported by the laser printer, the present invention measures a single reaction force from the developer housing. The magnitude of this reaction force is then correlated to the amount of toner in the developer housing of the removable toner cartridge.
The reaction force is minimally affected by mechanical noise variables. The mechanical noise variables are due to varying forces over which there is no control except within a specific range.
The developer housing is slidably received in a cleaner housing of the removable toner cartridge and is resiliently connected thereto by two bias springs on opposite sides of the developer housing being connected to opposite sides of the cleaner housing so that the developer housing can roll or slide in the cleaner housing. These two bias springs have standard manufacturing tolerances that result in significant variation from spring to spring.
Accordingly, it is necessary to decrease the vertical component of the force created on the developer housing by the varying spring forces to a minimum. This is accomplished by disposing one of the bias springs at a relatively small angle to a line connecting the centers of the developer roll and the photoconductive drum such as 2°-4°, for example, and the other of the bias springs at a slightly larger angle to the line connecting the centers of the developer roll and the photoconductive drum such as 22°-24°, for example. It should be understood that the line connecting the centers of the developer roll and the photoconductive drum is at a slightly inclined angle to the horizontal because of the geometry of the removable toner cartridge.
The bias spring having the smaller angle is attached to the side of the developer housing transmitting the reaction force. This creates a negligible vertical component so that it does not have an effect on the magnitude of the transmitted rear reaction force since the transmitted rear reaction force is substantially vertical.
In determining forces acting on the developer housing, each side of the developer housing must have its forces treated independently. All the forces acting on the developer housing are used to determine the magnitude of the rear reaction force.
In the present invention, maximum and minimum mechanical noise level variables are determined. Then, using all of the combinations of every mechanical noise variable at both its minimum and maximum levels, the desirable mechanical parameters are determined that would result in the noise variables producing a minimum effect on the rear reaction force when determining the maximum level of toner. This same mechanical noise variation remain at the same values for other levels of toner because the mechanical noise variation is independent of the toner level.
Accordingly, the statics of the developer housing as a free body are mathematically and experimentally optimized to have the measured rear reaction force as closely related to the toner weight in the developer housing as possible and the effect of the mechanical noise variation minimized. That is, the magnitude of each
Merrifield David Lee
Newman Benjamin Keith
Brady John A.
Lexmark International Inc.
Pendegrass Joan
LandOfFree
Removable toner cartridge does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Removable toner cartridge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Removable toner cartridge will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2436095