Patent Application
20050285887
1. Field of Invention
This invention generally relates to systems and methods for determining a printhead in a printing position.
2. Description of Related Art
A typical imaging apparatus, such as an ink-jet printer or a thermal printer, forms an image onto a recording medium, such as paper or film, by causing ink or the like to be deposited onto the recording medium. For example, an ink-jet printer performs printing by discharging ink through a printhead having nozzle(s) with an orifice and an electrothermal transducer which generates discharge energy for discharging ink from the orifice to form a pattern of ink dots on the recording medium. The printhead discharges the ink along a track by moving back and forth. Many printheads must also move toward and away from a printer's surface. However, the movement of the printhead may get trapped, jammed or wedged along the way. For example, in certain solid ink printing, the printhead is moved between printing, wiping and standby positions. If the printhead is not properly positioned, ink may be misdirected.
Thus, in the past, a separate sensor was required to determine the position of the printhead so that the ink could be properly ejected onto the recording medium.
For example, conventional printers use an optical sensor to ensure proper positioning of the printhead. However, separate sensors require numerous cablings and connectors to operate. Further, many printers typically have more than one sensor to determine positioning of the printhead, especially apparatus with color inks. Thus, the use of sensors becomes expensive, which drives the cost of manufacturing up. Moreover, because of the need for cables and connectors to operate the sensors, printing apparatus become large and bulky.
Considering the above conventional drawbacks, it is desired to provide a printing apparatus control method which can efficiently determine the position of the printhead without the need of separate, standalone sensors.
Accordingly, one aspect of the invention provides systems and methods for determining a printhead in a printing position without the use of standalone sensors.
One exemplary embodiment according to the systems and methods of the invention include use of electrical signals from a motor while the printhead assembly moves over a head tilt cam to determine if the printhead has properly tilted to a print position.
Another exemplary embodiment according to the systems and methods of the invention includes tilting the printhead from the standby position to the print position, sampling the electrical signal that measures torque from the motor that tilts the printhead at two positions, and calculating the slope of the signal between the two positions. The slope is then compared against a predetermined slope threshold to determine whether the printhead has properly tilted.
In various exemplary embodiments of the systems and methods according to the invention, the first and second electrical signals measure resistance force on the motor.
In various exemplary embodiments of the systems and methods according to the invention, the printhead is determined to operate properly when the calculated slope is above the predetermined threshold, for example, a positive slope.
In further various exemplary embodiments of the systems and methods according to the invention, when the cam rotates and tilts the printhead, a resistance on the motor is sensed as the motor stops at two positions on the cam. A slope is then calculated between the two sampled electrical signals and compared against a predetermined threshold.
In various exemplary embodiments of the systems and methods according to the invention, the first position samples the electrical signal at a low resistance area on the cam.
In various exemplary embodiments of the systems and methods according to the invention, the second position error is samples the electrical signal at a position on the cam that is steep giving high resistance.
In various exemplary embodiments of the systems and methods according to the invention, the slope is a calculation between the steepness of the two sampled electrical signals.
In various exemplary embodiments of the systems and methods according to the invention, a tilting arm provides movement to the printhead in different positions.
In further various exemplary embodiments of the systems and methods according to the invention, the different positions are a standby position, a wipe position, P1, P2, and a home/print position. P1 and P2 are two points on the cam where the electrical signals are sampled, from which the slope is calculated.
In various exemplary embodiments of the systems and methods according to the invention, the sensed electrical signal is a measure of motor torque.
These and other features and advantages of the invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.
Various exemplary embodiments of the systems and methods of this invention will be described in detail, with reference to the following figures, wherein:
As an exemplary embodiment, the printing apparatus 100 is a solid-ink printer, for example, a Xerox 8400 printer. However, the invention is not limited to this and is applicable to any type of printing apparatus having a reciprocating or movable printhead.
In solid-ink printing, the printhead 110 ejects an ink onto the rolling drum 140 that transfers the ink onto a recording medium, for example, but not limited to, paper, labels, transparencies, envelopes and business cards. The printhead 110 has an array of nozzles that can jet out a predetermined quantity of ink into the surface of drum 140 as known in the art.
The cam following arm 120 provides movement to the printhead 110 enabling the printhead 110 to be positioned in various positions either closely adjacent to drum 140 or away from drum 140. This is achieved by engagement with the cam 130.
In an exemplary embodiment, the different positions are a standby, a wipe, P1, P2, and a home/print position. In the standby position, the cam following arm 120 moves the printhead 110 in a position that is tilted away and farthest from the rolling drum 140. In the wipe position, the cam following arm 120 moves the printhead 110 to a position where it can be engaged with a wiping device, such as, for example, a wiper blade. In the print/home position, the cam following arm 120 moves the printhead 110 close to the rolling drum 140 so that the ink can be applied on the drum 140. Positions P1 and P2 are the locations on the cam where the electrical signals are read to calculate the slope.
The cam 130 includes gear train 150 to drive the cam 130 via motor 160 having mating gear teeth. An exemplary motor is a servomotor. The print head tilt servomotor provides data to the controller that is related to the movement of the motor. If the torque is high or low the feedback gives the controller the information to make corrections, for example to keep a constant velocity. The positions on the cam where this feedback is read are designed to show a low and high resistance, from which the slope is calculated. This same feedback could be used in other cam designs, to show resistance and profile. Upon activation of drive motor 160, cam 130 rotates, which causes cam following arm 120 to move relative to the cam 130 to cause printhead 110 to tilt from the shown standby position to either a wipe position or a print position. Electronic signals of the motor 160 are sampled at cam locations P1 and P2. The position P1 corresponds to a time when the cam following arm 120 should be in contact with an area on the cam 130 that is not steep. During the sampling at P1, there will not be much spring force. As such, resistance acting on the drive motor should be low. The sampling at P2 corresponds to a time when the cam following arm 120 should be in contact with an area on the cam 130 that is steep. During the sampling at P2, there will be more spring force as higher resistance is needed to hold the tilt arm position on the cam. As such, resistance acting on the motor is higher. Processing means 180 then analyzes the electrical signals by calculating the slope between the two position samples to determine whether the printhead 110 is at a desired location.
As an exemplary embodiment, the various tilt phases are positions of the printhead 110 in relationship to the cam 130. For example, the various tilting phases of the printhead 110 are a standby position, a wipe position and a home/print position, and various intermediate positions.
As shown in
In various exemplary embodiments, position P1 occurs when the arm 120 is in contact with a flatter location on the cam 130 where there is not much resistance force (low torque), and position error P2 occurs when the cam following arm 120 is in contact with the cam 130 right before a steeper part on the cam 130 so as to cause more resistance force (high torque). As shown in
As shown in
However, as shown in
It should be appreciated that the resistance during the tilting of the printhead is generally higher when the printhead 110 is operating properly than when the printhead 110 is not operating properly. However, for different cam 130 profiles, the values can be changed. What is important is that there is a known slope threshold that signifies improper operation of the printhead assembly.
If it is determined at step S200 that the printhead 110 is not tilted in the standby position, operation continues to step S300 which terminates the checking of the position of the printhead 110. On the other hand, if it is determined at step S200 that the printhead 110 is at the standby position, operation proceeds to step S400.
In step S400, the operation moves the headtilt of the printhead 110 from the standby position to the printing position. In various exemplary embodiments, the printing position is when the printhead 110 is properly positioned relative to a printing surface, such as rolling drum 140.
At step S500, the engaged printhead 110 stops the motor 160 to sample the electrical signal at P1 on the cam 130. In various exemplary embodiments, position P1 is a flatter location on the cam 130 where there is not much resistance force. Operation then proceeds to step S600.
In step S600, the operation samples the motor 160 electrical signal, such as motor torque, and saves the samples for P1. Operation then proceeds to step S700.
At step S700, the operation restarts the motor 160 to tilt the printhead and stop at position P2. At step S800, the process samples the motor 160 electrical signal, such as motor torque, and saves the samples for P2. In various exemplary embodiments, position P2 is the location on the cam 130 adjacent to the large steep part of the cam that causes a higher resistance force, in order for the printhead to keep its position. Operation then proceeds to step S900.
At step S900, the operation finishes tilting the printhead 110 to the print/home position, and proceeds to step S1000 to calculate the slope using P1 and P2 electrical signal samples. In various exemplary embodiments, the slope is calculated by calculating the difference between the two samples P2 and P1.
In various exemplary embodiment, if the slope is above or equal to the designated threshold, the operation indicates that the printhead 110 is tilting over the cam 130 in proper working order. In a further various exemplary embodiment, if the slope is below the designated threshold, the operation indicates that the printhead 110 is not tilting over the cam 130 in proper working order. For example, but not limited to, the printhead 110 is jammed and unable to tilt. If the calculated slope is below the threshold there is less resistance on the motor 160 than should be as the printhead 110 moves over the cam 130.
If it is determined at step S1100 that the slope between P1 and P2 is above or equal to the designated threshold, the operation continues to step S1200 which terminates the operation and indicates the tilting of the printhead 110 to the home/print position was successful. On the other hand, if it is determined at step S100 that the slope between P1 and P2 is below the designated threshold, operation proceeds to step S1300.
At step S1300, the operation determines that the printhead 110 did not properly tilt to the home/print position, and repeats the operation at step S200. An error or other indicator may be provided to alert the user to the problem.
While the invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made to the invention without departing from the spirit and scope thereof.
