Determining initial position of an ink-jet printer head and protecting against capping release errors

Abstract: An apparatus for determining an initial position and protecting against capping release errors in an ink-jet printer head is described. The apparatus includes a home sensor 40 arranged on a frame 10, a first actuator 50 disposed on the right hand side of the carriage 20, for sensing an initial position of the carriage 20 when power to the printer is turned on or a printing command is issued and a second actuator 60 disposed on the left hand side of the carriage 20, for sensing a capping state when the carriage has moved to a service interval. This second actuator is used to control the position of the carriage, to prevent the capping state from being released.

Description: BACKGROUND TO THE INVENTION The present invention relates to an ink-jet printer, and more particularly, to a method of determining an initial position and protecting against capping release errors. Generally, printers which have a printing head mounted on a carriage have used various methods for determining the current printing position of the head: for example, recognizing a reference position using an encoder; and memorizing the distance moved from a reference position using a home sensor at a predetermined position. The encoder method has the problem of high production cost because the encoder is expensive. The home sensor method has a problem in that production cost is high because a fine stepping motor is used. FIG.1 is a schematic view of the construction of a conventional initial position determining and capping release error protecting apparatus. In this construction, a home sensor 1 is usually an optical sensor or microswitch and a single actuator 2 is disposed on a carriage 3 and activates the home sensor 1 to determine a reference position. Whenever the control for the reference position is executed during a printing operation, the home sensor 1 is adapted to sense the actuator to avoid deviation of the reference position. So as to control the reference position during the printing operation, when the actuator 2 moves to the home sensor 1, the carriage 3 moves up to a service station 4, such that the carriage 3 comes into contact with the components of service station 4, which results in noise. Accordingly, the reference position should be set in such a manner that the carriage 3 is placed to the left of the capping position. The carriage 3 performs a round trip within a print interval, and the carriage is moved to the capping position towards a service interval by a distance determined on the basis of mechanical design, after the home sensing is executed. It is, however, difficult to prevent a capping release error with a home sensor 1 and an actuator 2, as shown in FIG.1. Since a cap 5 made of a rubber material is structured to perform a capping operation within an interval (3mm or more) in which the cap 5 may deviate during capping a nozzle 31, the sensor 1 and actuator 2 have great difficulty in simultaneously sensing an initial position and detecting a capping release error. Accordingly, a sensing device is needed to determine the initial position during the printing operation and a further device for preventing the capping state from being released is required while the head 6 is at the service station 4. However, while the capping state is kept up, if the head 6 is moved toward the print interval, due to an external impact or an unexpected external force, and thus a capping release error is undesirably generated, it is impossible to return the head to the capping state, so that the nozzle 7 of the head 6 may dry and will finally be blocked. JP-A-05077434 describes a printing position controller that includes a plurality of uniformly spaced sensor devices. A printer carriage includes an index strip that is slightly longer than the distance between the sensors, so that two and at most two of the sensors can detect the presence of the index plate. This device is stated to increase accuracy of the carriage location and increases in the width of the printing area can be accommodated easily by increasing the number of sensors. JP-A-60 099 679 discloses an ink-jet printer according to the preamble of claim 1, and a method according to the preamble of claim 7. In particular, JP-A-60099679 shows a position sensor that consists of a stationary element and a component that is attached to the carriage. That component includes a first lug, detected by the sensor element when the carriage is in an home position and a second lug, detected by the sensor element 7 when the carriage is in a capping position. The lugs are separated by a space. The present invention is directed to an improved apparatus and method for determining an initial position and for protecting a capping release error in an ink-jet printer head that addresses the problems described. SUMMARY OF THE INVENTION Accordingly, the present invention provides an ink-jet printer comprising: first and second sensor components, one mounted on a fixed part of the printer and the other on the printer carriage, such that the first and second sensor components are in proximity to one another and generate a first sensing signal when the carriage is in an initial position and a second sensing signal when the carriage is in a service interval and control means for controlling the carriage in response to the first and second signals; characterised in that the control means is adapted to determine whether the carriage is in a capping state in the service interval after the carriage is stopped, to determine from the second sensing signal whether the carriage remains in the service interval while in the capping state and, if the carriage has not remained in the service interval, to return the carriage to the service interval. In a first preferred embodiment, the second sensor component comprises two discrete portions; the first sensor component and one portion of the second sensor component are in proximity to one another and generate a first sensing signal when the carriage is in an initial position; and the first sensor component and the other portion of the second sensor component are in proximity to one another and generate a second sensing signal when the carriage is in a service interval. In an alternative embodiment, the first sensor component and one edge of the second sensor component are in proximity to one another and generate a first sensing signal when the carriage is in an initial position; and the first sensor component and the other edge of the second sensor component are in proximity to one another and generate a second sensing signal when the carriage is in a service interval. Preferably, the first sensor component is mounted on the fixed part of the printer and the second sensor component is mounted on the carriage. Preferably, the first sensor component is an active sensor component and the second sensor component is a passive sensor component. For example, the second sensor component may comprise one or more sensor actuators. The present invention also provides a method of protecting against capping release errors an ink-jet printer head which includes first and second sensor components, one mounted on a fixed part of the printer and the other on the printer carriage, such that the first and second sensor components are in proximity to one another and generate a first sensing signal when the carriage is in an initial position and a second sensing signal when the carriage is in a service interval, the method being characterised by : determining whether the carriage is in a capping state in the service interval after the carriage is stopped; determining from the second sensing signal whether the carriage remains in the service interval while in the capping state; and if the carriage has not remained in the service interval, returning the carriage to the service interval. Preferably, if the carriage has not remained in the service interval, it is returned to the service interval after a delay of about 20 to 30 seconds. Preferably, the method further comprises, after the carriage has been returned to the service interval, checking whether the head has been changed. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described by way of example with reference to the accompanying drawings in which: FIG.1 is a schematic view of the construction of a conventional initial position determining and capping release error protecting apparatus; FIG.2 is a schematic view showing a construction of an initial position determining and capping release error protecting apparatus; FIG.3 is a side view showing main parts of FIG.2; FIGS.4A AND 4B are views showing preferred embodiments of an initial position determining and capping release error protecting apparatus according to the present invention; FIG.6 is a flow-chart showing a capping release error protecting method according to the present invention; and FIG.7 is a flow-chart showing an initial position determining method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGs. 2 to 5, an explanation of the construction of the initial position determining and capping release error protecting apparatus will be discussed. A home sensor 40 is arranged in a frame 10, for sensing the initial position and a capping release error of a carriage 20 to transmit a sensing signal to a controller 80. A first actuator 50 is disposed on the right side of the carriage 20, for sensing an initial position of the carriage 20, when power in the printer is turned on or a printing command is issued. A second actuator 60 is disposed on the left side of the carriage 20 and passes the home sensor 40, to maintaining the state where a cap 71 is capped onto a nozzle 31 of the head 30 after the carriage 20 has moved to a service interval and for controlling the position of the carriage 20, to prevent the capping state from being released. In FIG. 4A, the sensing operation of the home sensor 40 is accomplished when both the first and second actuators 50 and 60 reach the home sensor 40. In FIG. 4B, however, the first and second actuators 50 and 60 are connected to each other to form a single actuator 140, so that when both ends of actuator 140 pass the home sensor 40, the home sensor 40 can sense the initial position. In this case, the controller 80 is programmed in such a manner than the sensing operation of the home sensor 40 can be accomplished only when both edges of the actuator 140 pass the home sensor 40. FIG.5 is a block diagram showing the hardware construction of the apparatus. A controller 80 controls the whole of the printer. A keyboard 90 is provided to receive and supply printing and capping signals to the controller 80. An external interface 100 is connected to the exterior, for interfacing the exterior with a communication port of the controller 80. A home sensor 40 senses the initial position and the capping state of a carriage 20 to transmit a sensing signal to the controller 80. A memory 110 holds input data for the controller 80. A motor driver 120 compares a signal from the home sensor 40 with the content of the memory 110 to drive a motor 121 under control of the controller 80. A head driver 130 compares the signal from the home sensor 40 with the contents of the memory 110 to actuate the head 30 under control of the controller 80. An explanation of the operation of the apparatus in an ink-jet printer head will now be given with reference to FIGs 2 to 5. When power to the printer is turned on or a printing command is issued, the carriage 20 in which the head 30 is mounted moves in to the right towards the home sensor 40. The first actuator 50 positioned in the right side reaches the home sensor 40 to set the reference position. The position of the carriage 20 is controlled using this reference position. Thus, a printing signal from the controller 80 is continually output to the motor driver 120 and the head driver 130 to perform a printing operation, and during the printing operation, when the first actuator 50 reaches the home sensor 40, the controller 80 re-sets the initial position to allow the next line to be printed. For the capping of the nozzle 31, the controller 80 transmits a control signal to the motor driver 120, so that the carriage 20 moves to the service interval. At this time, when the first actuator 50 passes the home sensor 40 and thus the second actuator 60 is adjacent to the home sensor 40, the nozzle 31 of the head 30 is capped by the cap 71 to maintain a seal. However, if the carriage 20 moves to the print interval due to an external impact or force, the nozzle 31 of the head 30 moves away from the cap 71 and the second actuator 60 moves away from the home sensor 40 so that a capping release error occurs. As a result, since the home sensor 40 cannot sense the second actuator 60, the controller 80 receives a signal from the home sensor 40 to drive the motor driver 120 and thus the carriage 20 returns to the service interval. Although the controller 80 is programmed in such a manner that the carriage 20 is placed in the service interval so as to maintain the nozzle 31 of the head 30 in a capping state. Since the position of the second actuator 60 is changed at the same time as the position of carriage 20 is altered due to the external impacts or forces, the controller 80 receives the signal of home sensor 40 and compensates the position of carriage 20 to maintain the capping state. Referring to FIG. 4B showing another embodiment of the present invention, the first and second actuators 50 and 60 are connected to each other to form the single actuator 140, so that when both ends of the actuator 140 pass the home sensor 40, the home sensor 40 can sense the initial position. Accordingly, it can be understood that one home sensor 40 and two actuators 50 and 60 can sense an initial position as well as a capping release error generated, so that the problem of dried ink can be solved to improve the quality of printing and production costs can be lowered owing to a simple system construction. As shown FIG. 6, the capping release error protecting method will now be described. First, when a capping starting button is entered, at step 601, the carriage 20 is stopped and a determination is made as to whether the position of the carriage 20 is in a capping state. At step 602, while the position of the carriage 20 is in the capping state, a detection is made as to whether the home sensor 40 senses the second actuator 60. If the home sensor 40 fails to sense the second actuator 60 due to a capping release error, a waiting operation is performed at step 603 for about 20 to 30 seconds to cater for the case where the user is holding the carriage 20. At step 604, when the position of the carriage 20 is moved by an external impact or the user, the position of the carriage 20 is compensated and the carriage 20 returns to its capping position. Next, at step 605, a detection is made as to whether the head 30 is in the returned carriage 20 or the head 30 is changed to a black or colour head. At step 606, the home sensor 40 senses the second actuator 60 or the type of the head 30 is checked and a normal state of the printer is input to the controller, thus completing a capping release error protecting operation. As shown FIG. 7, an the operation of the initial position determining method will now be described. At step 710, a determination is made as to whether the head 30 mounted on the carriage 20 is performing a printing operation. Then, at step 711, if the head 30 is involved in a printing operation, a determination is made as to whether the performance requirements for checking a reference position is satisfied. If satisfied, at step 712, movement of the first actuator 50 disposed in a right side of the carriage 20 to the right is made to sense the home sensor 40 and the reference position is set. If not satisfied, however, the method returns to the step 710. At step 713, next, the position of the carriage 20 is controlled using the set reference position, to determine an initial position of the carriage 20. As discussed above, the present invention provides an apparatus and method for determining an initial position and protecting against capping release errors in an ink-jet printer head. Therefore, one home sensor and two actuators can simultaneously sense an initial position while printing as well as a capping release error, so that the problem of ink drying can be solved to improve the quality of the printed image and production costs can be lowered owing to the simple construction of the system.

Claims: An ink-jet printer comprising: first and second sensor components (40, 50, 60; 40, 140), one mounted on a fixed part (10) of the printer and the other on the printer carriage (20), such that the first and second sensor components are in proximity to one another and generate a first sensing signal when the carriage is in an initial position and a second sensing signal when the carriage is in a service interval and control means (80) for controlling the carriage (20) in response to the first and second signals; characterised in that the control means (80) is adapted to determine whether the carriage (20) is in a capping state in the service interval after the carriage (20) is stopped, to determine from the second sensing signal whether the carriage (20) remains in the service interval while in the capping state and, if the carriage (20) has not remained in the service interval, to return the carriage (20)to the service interval. An ink-jet printer according to claim 1 in which: the second sensor component comprises two discrete portions (50, 60); the first sensor component (40) and one portion of the second sensor component (50) are in proximity to one another and generate a first sensing signal when the carriage (20) is in an initial position; and the first sensor component (40)and the other portion of the second sensor (60) component are in proximity to one another and generate a second sensing signal when the carriage (20) is in a service interval. An ink-jet printer according to claim 1 in which: the first sensor component (40) and one edge of the second sensor component are in proximity to one another and generate a first sensing signal when the carriage (20) is in an initial position; and the first sensor component (40) and the other edge of the second sensor component are in proximity to one another and generate a second sensing signal when the carriage (20) is in a service interval. An ink-jet printer according to any preceding claim in which the first sensor component (40) is mounted on the fixed part (10) of the printer and the second sensor component (50, 60; 140) is mounted on the carriage. An ink-jet printer according to any preceding claim in which the first sensor component (40) is an active sensor component and the second sensor component (50, 60; 140) is a passive sensor component. An ink-jet printer according to claim 5 in which the second sensor component comprises one or more sensor actuators. A method of protecting against capping release errors an ink-jet printer head which includes first and second sensor components (40, 50, 60; 40, 140), one mounted on a fixed part (10) of the printer and the other on the printer carriage (20), such that the first and second sensor components are in proximity to one another and generate a first sensing signal when the carriage (20) is in an initial position and a second sensing signal when the carriage (20) is in a service interval, the method being characterised by: determining whether the carriage (20) is in a capping state in the service interval after the carriage is stopped; determining from the second sensing signal whether the carriage (20) remains in the service interval while in the capping state; and if the carriage (20) has not remained in the service interval, returning the carriage to the service interval. A method according to claim 7 in which, if the carriage (20) has not remained in the service interval, it is returned to the service interval after a delay of about 20 to 30 seconds. A method according to claim 7 or claim 8 further comprising, after the carriage (20) has been returned to the service interval, checking whether the head (30) has been changed.

Inventors: CHOENG SANG-WON, HA JONG-HO, LEE YONG-DUK, CHOENG, SANG-WON, HA, JONG-HO, LEE, YONG-DUK
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1996
Main classification: B41J2
IPC codes: B41J2, B41J19