EP0640491A2 - Method and apparatus for monitoring the operational state of an ink ribbon in a printer, particularly in a travel agency printer - Google Patents

Abstract

The invention relates to a method and an apparatus for detecting the operational state of an ink ribbon in a printer, in particular in a printer in a travel agency. The said ink ribbon is conveyed via an electric rotary actuator motor which is connected to the drive shaft of an ink ribbon cartridge, the magnitude of the transmitting drive force being inferred from the current taken up by the rotary actuator motor. According to the invention it is proposed that predetermined threshold values of the current characteristic (12) are detected during a measuring period (11) in which the rotary actuator motor (4) is operated in a pulsed manner, that, during this process, the value of the motor current pulse is compared with the threshold value in an evaluation unit (7), and that whenever the threshold value is exceeded a change in level takes place at the output of the evaluation unit (7) so that the resulting clock sequence is counted in a microprocessor (8) and used for the measurement result and for a display which is dependent thereon. <IMAGE>

Description

It is known to use a method for recognizing the functional state of an ink ribbon in a printer, in particular in a travel agency printer, in which the ink ribbon is transported via an electric rotary drive motor connected to the drive shaft of an ink ribbon cassette and the size of the current is taken up by the rotary drive motor the transmitted driving force is closed (document will be added later). In the known methods sensors, sensors or switches are required which are sensitive to temperature fluctuations, shocks or contamination. In addition, a comparison, adjustment procedure or adjustment is necessary for the corresponding devices or circuits. Further disadvantages of the prior art result from the fact that, for example, a ribbon break, poor ribbon tension, a complete blockage of the ribbon or defective drive electronics cannot be determined due to the known switches.

The invention specified in claim 1 addresses the problem of performing a detection of the ink ribbon and at the same time the ink ribbon drive elements due to the increasing current in a (direct current) rotary drive motor without measuring the current values.

• das Farbband fehlt oder ist gerissen
• das Farbband ist vorhanden und läuft normal
• das Farbband ist völlig blockiert.

The advantages achieved with the invention consist in particular in the fact that the following features can be distinguished primarily:

• the ribbon is missing or torn
• the ribbon is present and runs normally
• the ribbon is completely blocked.

Thus, the lack of the ribbon cassette can be determined, the tear of the ribbon, the complete blockage of the ribbon, insufficient tension of the ribbon and also whether the ribbon drive motor is defective or not connected at all, the drive electronics or the wiring are defective or whether the ribbon cassette is out the bracket has slipped. For this it is also advantageous that no further sensors, transmitters or switches are required, but that existing circuit areas can be used, which is very inexpensive. The system is also insensitive to temperature fluctuations, shocks or dirt, and the electronic effort can be kept correspondingly low. No adjustment, no setting procedure and no adjustment is necessary during assembly. So there is hardly any function to be checked, that would not have been captured.

According to further features of the invention, it is provided that the threshold value is determined in such a way that it is only reached in the start-up phase of the rotary drive motor or when the rotary drive motor is blocked. The measuring process therefore consists of switching on the ribbon motor for a limited time and evaluating the generated clock sequences. Due to the periodic switching on of the motor, the back emf has an effect with increasing speed and reduces the inrush current so that it no longer reaches the threshold value.

It is advantageously provided that the measurement is triggered by switching on the printer and / or by closing a printer housing. When a printer is operated, the ribbon is checked first.

In order to avoid a special quality of the rotary drive motor, of course such a rotary drive motor could also be used, which would be correspondingly more expensive, it is provided that the measuring duration, pulse frequency and duty cycle are matched to the rotary drive motor. This solution therefore does not require a minimal number of copies in the rotary drive motor used and also not in the mechanical connections to the ribbon cassette (gearbox, translation, etc.). Nevertheless, it is possible to determine the optimal pulse frequency and an optimal pulse-pause ratio.

Another embodiment of the invention is that the period of the switch-on cycles and the duty cycle of the rotary drive motor are optimized so that the rotary drive motor reaches a minimum speed before it is energized again.

Further features of the invention consist in that the functional state of the ink ribbon or the ink ribbon cassette is measured as a function of a predetermined number of cycles.

It is advantageous here that the ribbon is classified as missing, torn or completely blocked at a lower number of cycles and that the ribbon is classified as present and mechanically correct at a higher number of cycles.

The device for recognizing the functional state of an ink ribbon in a printer, in particular in a travel agency printer, the ink ribbon being guided endlessly in an ink ribbon cassette and the ink ribbon cassette having a drive shaft which is connected to an electric rotary drive motor, is designed in such a way that the pulsatingly operable rotary drive motor is connected to an evaluation unit for predetermined threshold value pulses, that the generated clock sequence or pulse sequence of the evaluation unit can be forwarded to a microprocessor, that the microprocessor is also connected to the motor driver circuit and that the motor driver pulses are sent to the rotary drive motor as on / off signals are conductive.

Fig. 1

ein Blockschaltbild mit Druckkopf, Druckwiderlager, Farbbandkassette, Auswerteeinheit, Mikroprozessor und Motortreiberschaltung,

Fig. 2

ein Diagramm des in eine Spannung umgewandelten Stroms, der durch den Drehantriebsmotor fließt,

Fig. 3

ebenfalls ein Spannungsverlaufsdiagramm, wobei der durch den Drehantriebsmotor fließende Strom jeweils bei jedem Einschaltimpuls den Schwellwert erreicht und

Fig. 4

ebenfalls ein Spannungsverlaufsdiagramm, wobei der durch den Drehantriebsmotor fließende der Strom sofort auf einen Maximalwert steigt.

An embodiment of the invention is shown in the drawing and will be described in more detail below. Show it:

Fig. 1

a block diagram with print head, print abutment, ribbon cassette, evaluation unit, microprocessor and motor driver circuit,

Fig. 2

1 shows a diagram of the current converted into a voltage which flows through the rotary drive motor,

Fig. 3

likewise a voltage curve diagram, the current flowing through the rotary drive motor reaching the threshold value for each switch-on pulse and

Fig. 4

also a voltage curve diagram, the current flowing through the rotary drive motor immediately rising to a maximum value.

1, an ink ribbon 1 is circulated through an ink ribbon cassette 2, the ink ribbon 1 being driven by a drive shaft 3 and a rotary drive motor 4, i.e. is transported. The ink ribbon 1 is guided around the tip of a print head 5, which is moved back and forth opposite a platen 6, the ink ribbon 1 being able to be clamped in, if the print head 5 is at a zero distance from the platen 6. The printers always contain a device for changing, adjusting or adjusting the distance between the print head 5 and the platen 6.

The rotary drive motor 4 is connected to an evaluation unit 7, which consists of a current detection (threshold value formation) 7a and a pulse generation 7b. The pulse generation is connected to a microprocessor 8 and this counts the pulses 10. In the microprocessor 8 there is a timer which switches the rotary drive motor 4 on and off under software control. The entire process is set up as a measuring period 11 (FIGS. 2 to 4) with a voltage profile 12.

Individual conditions occurring in practice will now be described, in which the errors mentioned regarding the ribbon, the ribbon cassette, the drive system and the like. occur:

1. The ribbon is missing

In the absence of ribbon 1, the rotary drive motor 4 is not loaded and can run freely.

The motor current profile 12 is shown in the upper half of FIG. 2. It can be clearly seen that the current in the start-up phase of the rotary drive motor 4 increases to its maximum value and then decreases with increasing speed until it is switched off. During this first switch-on pulse, the current reaches the set threshold value and runs through it several times. The cycle sequence 13 generated thereby can be seen in the lower half of the figure.

The clocks of the clock sequence 13 are evaluated in the microprocessor 8, more precisely counted. The number depends on the smoothness of the current curve and thus directly on the electromechanical properties of the rotary drive motor 4.

Already with the second switch-on pulse and with all others, the counter-EMF is so large that the set threshold is far from being reached.

2. The ribbon is torn

If the ribbon 1 is torn, the rotary drive motor 4 is only slightly loaded by the mechanics of the ribbon cassette 2 (gears, rollers, shafts, etc.), but this has hardly any effect on the current curve (current profile 12). The signal curve corresponds to FIG. 2.

3. The ribbon is present

Because the ink ribbon 1 is clamped between the print head 5 and the platen 6 during the measurement, the rotary drive motor 4 can no longer run freely.

The current curve in FIG. 3 differs significantly from the current curve according to FIG. 2 and reaches the threshold value with every switch-on pulse.

The falling current profile curve shows that the rotary drive motor 4 can still rotate freely for a certain time at the beginning of each switch-on process, despite the fact that the ink ribbon 1 is pinched. This is due to the tightening of the ink ribbon 1 in the ink ribbon cassette 2.

As can be clearly seen, at least the number of cycles that are generated without a ribbon in total are generated with each switch-on pulse. This process means that the number of cycles with ribbon 1 present is at least 6 times higher (six switch-on pulses) than without ribbon 1. By increasing the number of switch-on pulses, the interference immunity of the method can be increased as desired, which is a further advantage.

4. The ribbon is present, but completely blocked (ribbon cassette 2 or drive defective).

It does not matter whether the ribbon 1 during the measurement is trapped or not because there is a complete block anyway. As shown in FIG. 4, the current immediately rises to its maximum value each time the rotary drive motor 4 is switched on, then does not drop as is the case according to FIGS. 2 and 3, but remains there until the switch-off takes place. The reason for this is that the motor shaft can no longer turn due to the blockage and therefore no back-emf is built up, which reduces the current.

The threshold value is reached with each energization process and remains exceeded until it is switched off. A total of six cycles are counted (six switch-on processes).

Taktzahl kleiner 20

Farbband fehlt, ist gerissen oder völlig blockiert;

Taktzahl größer 60

Farbband ist vorhanden und mechanisch in Ordnung.

In summary it can be stated that the condition of the ribbon can be determined depending on the number of cycles:

Number of bars less than 20

Ribbon is missing, torn, or completely blocked;

Number of cycles greater than 60

Ribbon is present and mechanically correct.

Reference list

1

Ribbon

2nd

Ribbon cartridge

3rd

drive shaft

4th

Rotary drive motor

5

Printhead

6

Pressure abutment

7

Evaluation unit

7a

Current detection / threshold value formation

7b

Pulse generation

8th

microprocessor

9

Motor driver circuit

10th

Motor driver impulses

11

Measuring time

12th

Current flow

13

Bar sequence

Claims (8)

Method for recognizing the functional state of an ink ribbon in a printer, in particular in a travel agency printer, which is transported via an electric rotary drive motor connected to the drive shaft of an ink ribbon cassette, the magnitude of the transmitted drive force being deduced in accordance with the current consumed by the rotary drive motor,
characterized,
that during a measuring period (11) in which the rotary drive motor (4) is operated in a pulsed manner, predetermined threshold values of the current profile (12) are detected, that the motor current value pulse is compared with the threshold value in an evaluation unit (7) and that if the threshold value is exceeded In each case there is a level change at the output of the evaluation unit (7), so that the resulting clock sequence is counted in a microprocessor (8) and used for the measurement result and a display dependent thereon. Method according to claim 1,
characterized,
that the threshold value is determined such that it is only reached in the start-up phase of the rotary drive motor (4) or when the rotary drive motor (4) is blocked. Method according to one of claims 1 or 2,
characterized,
that the measurement is triggered by switching on the printer and / or by closing a printer housing. Method according to one of Claims 1 to 3,
characterized,
that the measuring duration (11), pulse frequency and duty cycle are matched to the rotary drive motor (4). Method according to one of claims 1 to 4,
characterized,
that the period of the switch-on cycles and the duty cycle of the rotary drive motor (4) are optimized so that the rotary drive motor (4) reaches a minimum speed before it is energized again. Method according to one of claims 1 to 5,
characterized,
that the functional state of the ink ribbon (1) or the ink ribbon cassette (2) is measured as a function of a predetermined number of cycles. Method according to claim 6,
characterized,
that at a lower number of cycles the ribbon (1) is missing, torn or completely blocked and at a higher number of cycles the ribbon (1) is classified as available and mechanically correct. Device for recognizing the functional state of an ink ribbon in a printer, in particular in a travel agency printer, the ink ribbon being guided endlessly in an ink ribbon cassette and the ink ribbon cassette having a drive shaft which is connected to an electric rotary drive motor,
characterized,
that the pulsatingly operable rotary drive motor (4) is connected to an evaluation unit (7) for predetermined threshold value pulses, that the generated clock sequence or pulse sequence of the evaluation unit (7) can be forwarded to a microprocessor (8), that the microprocessor (8) also the motor driver circuit (9) is connected and that the motor driver pulses (10) can be conducted as on / off signals to the rotary drive motor (4).

Images