1. Field of the Invention
The invention concerns a measuring arrangement and a measurement method to determine the play of a cartridge pivot unit of an inkjet printing system. The method serves to detect and compensate for age-dependent variations of the play and to assess whether the required precision in the pivoting of the cartridge pivot unit into the printing position can still be maintained. The invention is used in printing devices with relative movement between an inkjet print head and the print item, in particular in franking and/or addressing machines and in other mail processing apparatuses.
2. Description of the Prior Art
Pivot movements of a print head are known from German Utility Model DE 200 12 946 U1.
An acceptance unit is known from DE 10062012 A1 for at least one inkjet print head that is arranged so that it can move in rotation around a rotation axis that lies parallel to the transport direction of mail pieces and that, driven by a motor and controlled by a microprocessor, can be selectively pivoted at least into one printing position and one service position. A service position at a sealing station is occupied after longer printing pauses for, among other things, clearing the print head.
A front view of the franking machine of the Centormail® type and its electronics were at least partially shown in the German Utility Model DE 20 2006 008952 U1 (“Arrangement to change customer data of a franking device”).
A pivot mechanism and a control device for pivoting into a cleaning and sealing position is shown for the same franking machine in DE 10 2005 052 150 A1 (“Device to clean an inkjet print head”).
A method and device for clearing an inkjet print head of an inkjet printing system are known from EP 1792955 A1, wherein at least one ink cartridge equipped with a print head is arranged in an acceptance unit that is also designated as a cartridge pivot unit. This is driven in steps by an actuator and can be selectively pivoted (controlled by a microprocessor) at least into a printing position and into a clearing position near the printing position. While it is possible for the cartridge pivot unit to be moved during the clearing, for the purpose of printing the printing position should be controlled as exactly as possible. The cartridge pivot unit has a rotation axle with a rotation angle transmitter with which the position achieved upon a rotation of the axle can be determined. The cartridge pivot unit can have too much play even given a correctly adjusted rotation angle transmitter, which can lead to a malfunction of the machine.
An object of the present invention is to provide a measuring arrangement to determine the play of a cartridge pivot unit and a corresponding measurement method, wherein testing evaluation) of the play is made possible in a simple manner and without opening the machine.
The measuring arrangement has a microcomputer that is connected with a rotation movement sensor and with the first motor for its activation to pivot the cartridge pivot unit. The first motor is charged with pulses of corresponding energy, controlled by said microcomputer. The cartridge pivot unit is pivoted dependent on the supplied energy by means of a gearing train arranged between the first motor and the cartridge pivot unit. The movement of the cartridge pivot unit does not ensue in conformity with the actuation by the first motor if play of the gearing train must first be overcome. The play is permitted to completely occur upon pivoting of the cartridge pivot unit onto a mechanical stop. Movement is no longer detected by the rotation movement sensor that supplies the measurement values. The microcomputer is provided to determine and evaluate measurement values. A microprocessor of the microcomputer is programmed (by a program stored in the program memory of the microcomputer) to reverse the rotation direction of the first motor and therefore the movement direction of the cartridge pivot unit at a first point in time, with the first point in time being reached when the play of the train of the cartridge pivot unit has been permitted to completely occur. The microcomputer loads a counter that counts pulses as of the first point in time and has a working memory to store the digitized measurement values determined immediately following. A digital comparator that compares the immediately following digitized measurement values serves to evaluate measurement values. The microprocessor of the microcomputer is programmed to stop the counter at a second point in time when the difference of the immediately adjacent digitized measurement values is greater than a threshold, or when the difference of the immediately adjacent digital measurement values in successive measurements rises or changes. The counter state is stored as “play” in the working memory.
A measurement method to determine the play of a cartridge pivot unit is based on generating pulses with which the drive is charged, driving the cartridge pivot unit, and determining measurement values corresponding to a pivoting of the cartridge pivot unit. The digital measurement values, measured by a rotation movement sensor (in particular a rotation angle transmitter) and generated by a converter, are supplied to a microcomputer for evaluation thereof. The microprocessor causes the rotation direction of the first motor (step motor) and therefore the movement direction of the cartridge pivot unit to be reversed at a first point in time (when the play of the train of the cartridge pivot unit has completely occurred) by resetting a count value of a counter to zero at the first point in time and, as of the first point in time; by counting pulses whose number corresponds to the rotation movement of the motor shaft of the first motor (step motor), and by storing the immediately following determined digital measurement values in the working memory, and by digitally comparing the immediately following digitized measurement values. At a second point in time the counter is stopped and the counter state is stored as “play” in the working memory. The second point in time is reached when at least one singular change is detected in which the difference of the immediately adjacent digital measurement values is greater than a threshold, or when a repeated change of the difference of the immediately adjacent digital measurement values is detected in successive measurements, wherein the difference tends to rise.
The rotation angle transmitter and the microprocessor controller that are already present in many printers are used to determine the play of the cartridge pivot unit in the measuring arrangement. The total angle magnitude that the rotation angle transmitter can detect is greater than the pivot range. Upon assembly of the inkjet printing system of a franking machine, the rotation angle transmitter is adjusted such that approximately equal angle magnitude margins are reserved at both ends of the pivot range. The play of the cartridge pivot unit is the sum of all plays of a worm gear pair. A mechanical stop on a frame of the inkjet printing system exists in the cartridge pivot unit both at a minimal position (printing position) and a maximum position (exchange position). If the measurement voltage that can be tapped at the rotation angle transmitter does not change although the first motor (step motor) is activated, the cartridge pivot unit has reached an extreme position, i.e. a fixed stop. Starting from one of these extreme positions, the microprocessor controller can determine a number of steps for a step motor to activate each position of the cartridge pivot unit in the pivot range. Nevertheless, the invention proceeds from a mobile stop that is formed by a cleaning and sealing station (RDS). The cartridge pivot unit is first pivoted in the direction of the exchange position and then the RDS is moved into the sealing position, such that the cartridge pivot unit subsequently pivoted into the sealing position ultimately rests on the RDS and is pressed against it by gravity. The play of the worm gear pair is caused (permitted) to completely occur through further steps of the step motor. If the flights of the worm (which are coupled in terms of actuation) and a worm gear (segment) thereby driven are then rotated in the opposite direction, the play of the worm gear pair must initially be overcome before the cartridge pivot unit actually departs (separates from) the RDS. The play results from the number of the steps of the first motor (step motor) that are needed to cause the cartridge pivot unit to actually move.
The invention has the advantage that the time duration of the pivoting of the cartridge pivot unit with the at least one inkjet print head from the exchange position into the sealing position to stop at the RDS and back again into the exchange position is short relative to a pivoting of the cartridge pivot unit onto the fixed stop in the printing position. The cartridge pivot unit is held by its inherent weight in the sealing position while the drive direction of the train is reversed. Until the cartridge pivot unit moves and is pivoted back into the exchange position, its play can be determined very precisely in an advantageous manner. The precision in the pivoting into the printing position is increased by taking this play into consideration, such that a fixed stop in the printing position at the frame of the inkjet printing system, that is provided to prevent an overrun of the printing position, could even be omitted.
A perspective view of a franking machine of the Centormail® type is shown in
A microprocessor of a microcomputer is programmed (by a program stored in the program memory of the microcomputer) to activate the first motor in order to drive the cartridge pivot unit 12 via a train by means of the first motor; and to activate the second motor to drive the cleaning and sealing station RDS which is moved into the sealing position; wherein the cartridge pivot unit 12 is pivoted from an exchange position into a sealing position and strikes the cleaning and sealing station RDS and is pressed against it as a result of being pivoted further. Evaluation of the play of the cartridge pivot unit begins with being pivoted away from the sealing position back into the exchange position at a first point in time and ends at a second point in time when the change of the measurement values representative of the play again conforms with the pulses that are measured at the input side at the train, i.e. conforms with step pulses by means of which the first motor is activated, wherein the first motor is a stepper motor.
A block diagram of a measuring arrangement with microcomputer to determine the play of a cartridge pivot unit is shown in
The rotation angle transmitter 125 is, for example, an absolute position encoder of the MPR 403 or PMR411 type by TWK-Elektronic GmbH which is connected with operating voltage with its yellow connection line and with ground potential with its green connection line. The analog component voltage U2 at the middle tap (red) of the voltage divider is converted by an analog/digital converter 32 into a digital data value X2 that is digitally processed further or stored. For this purpose, the analog/digital converter 32 is connected at the output side with the digital inputs of a microcontroller (PC) 33. The analog/digital converter 32 and the microcomputer (microcontroller) 33 are components of the microprocessor controller that is used to determine the play of the cartridge pivot unit. The microcontroller furthermore has a program and data memory. A number of sensors and actuators are connected to the microcontroller (μC) 33.
A first motor M1 (124) to drive the cartridge pivot unit, a second motor M2 (1315) to drive the RDS 13 and a third motor (not necessary for measurement) to drive a mail piece transport device (not shown) are connected to the output side of the microcontroller. The first motor M1 (124) with its motor shaft is connected without slippage to, or is mechanically identical with, the shaft 1230 of a worm gear pair 123. The shaft 1230 carries a worm 1231 and is supported on both sides of the worm 1231 in ball bearings 1232 and 1233 that are subject to a play A of approximately 50 to 1000 μm.
The teeth of a worm gear or of a worm gear segment 1234, which is supported such that it can rotate around an axle 121, engage the flights of the worm 1231. Both the attachment and the teeth can exhibit a play of approximately 50 to 300 μm upon engagement in the screw. The cartridge pivot unit supported such that it can rotate on the axle 121 is mechanically connected without slippage with a potentiometer of the rotation angle transmitter 125. As soon as the cartridge pivot unit is rotated on the axle 121, the rotation angle transmitter 125 outputs at its middle tap a (normally modified) measurement voltage U2. No further change in the rotation angle can occur upon reaching the extreme positions and the sealing position. Upon moving the cartridge pivot unit with the first motor M1 (stepper motor) a certain play P occurs dependent on the respective position. This means that the stepper motor moves by a few steps before the component voltage at the rotation angle transmitter 125 (and the digital value resulting from this) changes. The play can be very large when
The play A of the worm 1231 occurs in the axial direction. Play B exists between the worm 1231 and the segment 1234 worm gear. For the following reasons it is necessary to know the play of the cartridge pivot unit:
Due to the use of a step motor 124, the necessity to detect the rotation of the motor axle at the input side at the train via an encoder E is advantageously dispensed with. The optional encoder and its connection lines are therefore drawn as a dash-dot-dot line. The analog/digital converter 32 can alternatively be an internal component of the microcomputer 33.
The measuring arrangement 30 according to
A presentation of the function of the microcomputer in the determination of the play of the cartridge pivot unit arises from
However, if the selectable, predetermined comparison value C is exceeded by the difference Δ, at Step 304 the workflow branches from the first interrogation step 302 for the purpose of storing the play P=Z in RAM 333. The value of the play P=Z can be output as needed via the input/output unit 334 for the purpose of display. If the criterion in the first interrogation step is satisfied, this means that the play P was overcome and that the change of the measurement values X2 again conforms with the step pulses.
A representation of the inkjet printing system with side view of a cartridge pivot unit from the left, rear, above is shown in
An adjustable stop 127 in the form of a bolt that can be screwed in is shown at the second wall plate 102 of the frame 10.
An edge 128 of the cartridge pivot unit 12 arranged on the hidden side of the base strikes this stop when said cartridge pivot unit 12 is pivoted into the other extreme position (not shown), i.e. the exchange position. A worm gear segment 1234 of the worm gear pair (not visible) which is arranged between the second wall plate 102 and the third wall plate 103 is attached on an end of a shaft (rotatable around the rotation axis 121) remote from the rotation transmitter 125. The first step motor 124 to drive the worm gear pair is arranged in an opening near the middle of the second wall plate 102.
A baffle plate 132 which is used when the cartridge pivot unit 12 is pivoted by 25.3° into a clearing position is attached by means of pivots 1321 and 1327 on the first wall plate (not shown) and on the second wall plate 102 such that it can rotate. A wheel 122 is fastened on the cartridge pivot unit 12 such that it can rotate and a guide edge 1323 is molded on a lateral rocker of the baffle plate 132. The baffle plate 132 is connected with the frame 10 via a tension spring 1322 which pre-stresses the baffle plate 132, whereby the wheel 122 non-positively rests on the guide edge 1323. A fastening pin 13221 that is connected with one end of the tension spring 1322 is mounted on the baffle plate 132. The wheel 122, the guide edge 1323 and the tension spring 1322 form a rocker (crank) guide for the baffle plate 132. The guide edge 1323 is advantageously formed on the left lateral rocker of the baffle plate 132. The at least one inkjet print head is pivoted into the printing position and the baffle plate 132 is lowered via the movement of the cartridge pivot unit 12. That occurs counter to the effect of the tension spring 1322, wherein the wheel 122 mounted on the cartridge pivot unit 12 engages with a guide edge 1323 of the left lateral rocker of the baffle plate 132 and is moved to the freely oscillating end of the rocker until the fastening pin 13221 arrives at an upper stop in a slot. An insert 1331 is provided below the cleaning and sealing device 13 for the accommodation of a fleece 13311.
A representation of the inkjet printing system is shown in
A flowchart for the measurement workflow is shown in
If the pivot device rests on the RDS and is pressed against it, the play of the worm gear pair is completely expressed. This leads to the situation that there is no longer any change of the measurement values X2 although additional step pulses are output by the microcontroller. No change of the measurement values X2 then ensues in conformity with the step pulses. If that is established in the second interrogation Step 414, the workflow branches to the sixth Step 415 for the purpose of carrying out a direction reversal and providing a fourth number of step pulses for the first step motor 124 to pivot the cartridge pivot unit out from the sealing position. A worm gear (segment) of the worm gear pair is thereby rotated in steps in the opposite direction and the cartridge pivot unit is thus moved away from the RDS. Moreover, a resetting of the count value Z:=0 of a counter C to zero ensues in a sixth Step 415. In a seventh Step 416 a step pulse is output to the first step motor 124 and the counter value of the counter C is incremented by the value “one”. Additional U2 measurements by means of the rotation angle transmitter 125, an A/D conversion and storage of the digital measurement values ensue in a subsequent eighth Step 127. The U2 measurements by means of the rotation angle transmitter 125, the A/D conversion and the storage of the digital measurement values X2 are continued until it is established in a third interrogation Step 418 that the change of the measurement values X2 again conforms with the step pulses, wherein the fourth number Z of step pulses counted at this point in time at the first step motor 124 yields the play P, which is stored in a subsequent ninth Step 419. However, if it is established in the third interrogation Step 418 that the change of the measurement values X2 does not conform with the step pulses, the workflow branches back to the beginning of the seventh Step 416 for the purpose of outputting an additional step pulse and incrementing the count value Z. After storing and display of the play P in the ninth Step 419, a stop Step 420 for the routine is reached. However, additional steps in order to move the cartridge pivot unit further into the exchange position can be executed (not shown) before a stop.
The invention is not limited to a present embodiment with a worm gear pair 123. Any other suitable train G can likewise be used.
The invention is also not limited to the present embodiment with a step motor. A direct current motor which is controlled with pulse duration-modulated field coil pulses could be used just as well as a first motor M1. An encoder E with an encoder wheel and associated light barrier is attached on the drive shaft 1230 of the direct current motor, which encoder wheel emits a number of pulses upon its rotation, which pulses can be counted by the microcomputer in order to determine the rotation of the motor drive shaft 1230 at the input side of the train G. The rotation movement sensor S1 can measure a rotation movement at the output side of the train G in analog and feed this to a converter that generates the digital measurement values. However, the converter is not necessary if a digital rotation movement sensor (for example here as well an encoder) is used to generate digitally countable pulses.
Other embodiments of the invention for other types of drive motors can thus clearly be developed based on fundamental ideas of the invention.
Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
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