EP0585676B1 - Franking machine - Google Patents

Description

The invention relates to a franking machine with a electrothermal printing device, with the stamp and / or image prints on it at a predetermined speed Postage passed by through image-wise distributed Transfer of color particles printed from a carrier tape be, according to the pictorial distribution heated by means of a thermal print head and thereby at the Printing device is passed, the thermal print head is opposed by a counter pressure element.

A printing device for a label printer is e.g. known from DE 39 35 348 A1. She works with you Thermal print head, the end face of which is designed as a print surface in which a straight row is electrically selective heatable transfer pins is arranged. These work when they are heated, so on what has passed them Carrier tape that the color particles present on it melt out with their binder and onto the print material can pass if this together with the carrier tape past the thermal print head. So with this Process a predetermined pressure between the print head and is the counter pressure element as one towards the print head with spring force acted upon counter pressure roller, which optionally in brought into an operating position or into a rest position can be.

If this principle is used in a franking machine, so the speed of work becomes selective Heating up the individual transfer pens of the thermal print head and the time required to cool them down. There were special control procedures for the thermal print head developed, causing a certain speed increase the printing process is possible, but with that a complication in particular of the necessary control circuit linked to an increase in costs for the Franking machine leads.

It is already electrothermal due to DE 21 00 611 C3 Known printing device in which the moving Carrier tape has a defined electrical resistance (so-called ETR tape), for which purpose a layer of electrical Resistance material is provided as a carrier for the color particles can be. The thermal print head has no electrical heatable transfer pins, but a series of printing electrodes or micro-contacts, which when the Carrier tape in connection with the resistance material and with selective control current flow through cause this towards a collecting electrode so that it selectively heats up and melts the color particles from the carrier tape and its transition to the printed material causes.

Because there are no transfer pens heated up on the printhead are cooled, a higher printing speed is possible, which is also faster with a franking machine could make possible. This could but have not yet been realized. The postal service has in contrast to a normal sheet-shaped recording medium due to bending, folding or irregular content usually a shape that changes over its length or one uneven printing area. Will it be through the print area a printing device operating with current flow through the carrier tape guided, so the print head with the carrier tape on the uneven surface e.g. an envelope not without faulty contact between its pressure electrodes and the carrier tape. This is expressed in dropouts in the printed image, and also Spark erosion can damage the pressure bar of the Thermal print head occur. Even if the thermal print head with strong spring force on the carrier tape or the Postal goods would be pressed or the counter-pressure element a resilient pressure of the thermal print head on the mail would produce some compensation for irregularities to achieve this would create new problems because pressing the thermal print head with one force of more than approx. 10 g per pressure electrode leads to an impermissible one high wear of the electrode surface and to a significantly reduce the possible useful life of a Thermal print head.

A franking machine is also from EP 0 298 774 A2 known whose thermal print head has heating elements that are selective heated according to the character to be printed, to print particles from the carrier tape onto the envelope transferred to. Opposite the thermal printhead is one Counter pressure roller arranged in a fixed position, with pressure rollers works together. The pinch rollers are on both sides the thermal print head arranged. If the one to be printed Surface is uneven due to bends, folds, etc. It may happen that the entire area is not covered with pressure particles of the carrier tape is applied. The print image then contains gaps or smears.

From US-A-4,626,873 a printhead holder is known which presses a thermal print head against a print carrier, which rests on a counter pressure roller. The printhead holder is pivoted in elongated holes, so that the Print head within certain limits in addition to the swivel movements Carry out lifting movements relative to the counter pressure roller can.

Furthermore, from US-A-4,553,861 a printer with a Thermal printhead known against a platen can perform pivoting movements under spring pressure. Swivel movements with a relatively large stroke by an electromagnet triggered. In a rest position, not in the is printed, the print head swivels when the Electromagnet back and gets out of engagement with one Thermal transfer ribbon. In the working position, the electromagnet actuated so that the print head on the thermal transfer ribbon rests and ink on a print carrier transmits.

In addition, it is known in the prior art (DE 34 17 381 A1) for automatic adjustment of a dot matrix print head a device to the thickness of a paper to be printed insert the thickness of the paper using a feeler roller scans. The deflection movement of the sensor wheel is transferred to a holder for the printhead, which is thus relative to a stationary thrust bearing emotional.

Through the US-A-4,924,240 a franking machine with a Known printing device, which is arranged in a stationary manner Thermal print head user. The one opposite the thermal print head Back pressure element is arranged so that it be moved towards and away from the thermal print head can. The counter pressure element becomes resilient against the printing the thermal print head and against guide rollers.

A franking machine is known from FR-A-2 519 583, where a counter pressure roller moves the mail against one Printing drum presses. In the starting position, with the still if no letter has reached the print area, the two lie Rolling the impression roller and the printing drum with their Surfaces on each other. The counter pressure roller is in one Frame stored, which is pushed down by the mail becomes. The contact pressure of the counter pressure roller must be so be chosen that even thick and unevenly run Letters captured by printing drum and platen roller and be moved through and the letter not in between stuck. This arrangement is based on the use of a tied rotating printing drum. The back pressure roller is resiliently stored and can be used as a printing drum take different angles.

It is an object of the invention, one with a equipped electrothermal printing device Specify franking machine that makes it possible to even uneven Print surfaces of the postal matter with high quality.

This object is solved by the features of claim 1.

In the invention, the contact surface of the counter-pressure roller tilt against the print bar of the thermal print head. This can affect the pressure force on the contact surface distribute evenly and a constant Create pressure along the length of the print bar. The printing elements of the thermal print head can thus energy evenly distribute distributed into the carrier tape so that its Also transfer the color evenly to the mail becomes.

For example, if a letter envelope contains a coin, so is avoided in the prior art that a postal jam occurs by the counter-pressure roller making an evasive movement in perpendicular to the direction of transport of the envelope Direction. The one generated by the back pressure roller Pressure against the thermal bar of the thermal print head is only high in the area of the coin, so that an irregular Color printing is generated. Because in other places reduced force initiated on the envelope there is even a risk that the position of the Force concentrated on the thermal print head becomes large and closes or even damages it becomes. In the invention, the contact surface nestles with different angles to the printing surface the thermal print head to the coin and practice outside the area of the coin. Thereby the print bar of the thermal print head always stays in Contact with most of the surface of the envelope, which ensures perfect color printing.

The invention can also be used for the ETR process (electro-thermal resistive process). be used where the Carrier tape has a resistive layer that acts as electrodes trained print elements of an ETR print head is heated according to a predetermined pattern. On The heated areas of the carrier tape are colored on the Transfer mail. The ETR method is relatively high Pressure forces are required to ensure a uniform print image receive. The object of the invention meets the high Requirements of the ETR procedure.

In a preferred embodiment, the backing roller is at their ends by a bellows with the Shaft non-rotatably connected. Such a bellows leaves on the contact surface of the counter pressure roller with the Press the mail together, the contact surface being different Angle also to the printing surface in the direction of transport can take. This causes the counter pressure roller to nestle even better at uneven places in the mail, so that the pressure is distributed evenly along the pressure bar becomes.

Another development is characterized in that the counter-pressure roller is mounted on a fork that with a holding element preferably connected by a swivel whose axis of rotation is at least approximately vertical to the longitudinal axis of the counter-pressure roller shaft and at least runs approximately parallel to the direction of transport of the mail. Through these measures, the back pressure roller can additionally Carry out swiveling movements around the axis of rotation, see above that even with relatively large items that the postal service are included and cause uneven surfaces, the contact surface of the counter pressure roller has a large angular stroke can perform without the pressure distribution on the Contact surface becomes uneven.

The aforementioned embodiment can be developed in this way be that the fork has at least two roles that the Counter-pressure roller on the side facing away from the thermal print head Side circumferentially at an angular distance from each other store rotatable. The outer surface of the counter-pressure roller supports down on the rollers while turning. This will make the bearing forces acting on the shaft are reduced.

In the invention, the Counter-pressure roller along one perpendicular to the direction of transport of the goods to be transported through an adjusting device adjustable. The actuator has two operating positions. The counter-pressure roller presses in one the postal matter under spring pressure against the printing surface of the Thermal print head; in the other takes the back pressure roller a rest position in which it is removed from the thermal print head is. These measures will make the thermal print head only when transporting mail with force through the counter-pressure roller acted upon.

Furthermore, the holding element mentioned above can be a elastic part, such as a coil spring included. This part clamps the fork in the direction perpendicular to Printing area in front. If the longitudinal axis of the shaft is stationary and the outer surface of the counter pressure roller Rollers is supported, so the spring force causes Bellows an eccentric deformation of the counter pressure roller towards the pressure bar. This can cause fluctuations in thickness of the postal items, e.g. in the range of 0 to 3 mm, balanced become.

A preferred embodiment of the invention provides one Presetting device that the counter-pressure roller on a Distance to the printing surface of the thermal print head depends of the thickness of the mail item. The back pressure roller still necessary to carry out the printing process Lifting motion is then relatively small Path, for example 3 mm, limited regardless of how thick is the postal matter to be printed. The devices for Adjusting the pressure roller can thus be relative for one short stroke can be optimized.

A further development of the aforementioned embodiment provides before that the postal matter on the way to the thermal print head is sensed by a sensor for thickness, the one Signal for controlling a presetting device Servomotor outputs if a predetermined thickness is exceeded. The predetermined thickness can e.g. 3 mm be. As a result, not every postal item is automatically an adjustment movement triggered, but only when the predetermined amount is exceeded. Since the number the adjusting movements of the presetting device are restricted overall, the franking machine can be fast and work reliably.

Figur 1

eine schematische Seitenansicht der wichtigsten Teile einer mit Transportmechanik für ein Trägerband arbeitenden Frankiermaschine als Ausführungsbeispiel,

Figur 2

den Längsschnitt einer Schwingenanordnung zum Halten zweier Andruckwalzen und eines Thermodruckkopfes im Druckbereich,

Figur 3

die Vorrichtung nach Figur 2 in perspektrivischer Darstellung,

Figur 4 bis 7

eine weitere Ausführungsform einer Frankiermaschine in schematischer Darstellung bei unterschiedlichen Betriebsstellung,

Figur 8

eine weitere Ausführungsform einer Frankiermaschine in schematischer Darstellung,

Figur 9

eine Ausführungsform mit verstellbarem Träger, der durch eine Klemmvorrichtung in seiner Höhe arretierbar ist,

Figur 10

ein Ausführungsbeispiel mit einer beweglich gelagerten Gegendruckwalze,

Figur 11

eine Stellvorrichtung zum Vertellen der Gegendruckwalze,

Figur 12

eine mit einem Zahnrad angetriebene Stellvorrichtung, und

Figur 13

eine Anordnung mit der die Gegendruckwalze auf unterschiedliche dicken des Postgutes voreingestellt werden kann.

The invention is explained below with reference to the drawing. In it show:

Figure 1

1 shows a schematic side view of the most important parts of a franking machine working with a transport mechanism for a carrier tape, as an exemplary embodiment,

Figure 2

the longitudinal section of a rocker arrangement for holding two pressure rollers and a thermal print head in the printing area,

Figure 3

2 shows the device according to FIG. 2 in a perspective view,

Figure 4 to 7

another embodiment of a franking machine in a schematic representation in a different operating position,

Figure 8

another embodiment of a franking machine in a schematic representation,

Figure 9

an embodiment with an adjustable carrier which can be locked in height by a clamping device,

Figure 10

an embodiment with a movably mounted counter-pressure roller,

Figure 11

an adjusting device for adjusting the counter-pressure roller,

Figure 12

an actuator driven by a gear, and

Figure 13

an arrangement with which the counter-pressure roller can be preset to different thicknesses of the postal matter.

In Figure 1, the working principle is schematically in a side view a franking machine, which according to the so-called ETR printing process, in which a Carrier tape for the color particles is used, the one has defined electrical resistance and therefore selective is heated. A current flow through the carrier tape headed by a pressure electrode Thermal print head over the carrier tape to a collecting electrode to be led. Figure 1 shows an ETR printhead 10, the is arranged behind a pressure roller 11. Another Pressure roller, which can not be seen in Figure 1, is located behind the thermal print head 10, so that two Pressure rollers are arranged on both sides of the thermal print head 10 are. The pressure rollers 11 form with a counter pressure roller 12, which is below them, each a transport gap for a letter.

The transport gaps are in the area of a conveyor path 13, at the beginning of the feed rollers 14 and 15 and at the end Ejection rollers 16 and 17 are arranged.

A letter is placed in the franking machine on the one with the feed rollers 14 and 15 formed feed gap. The feed rollers 14 and 15 are shown in the Driven in the direction of the arrow and then convey the letter in the transport column, which with the pressure roller pair 11 and the pressure roller 12 are formed. Because the back pressure roller 12 coupled to the rotary drive of the franking machine the letter is through the print area of the thermal print head 10 passed and then arrives after the printing process in the gap between the ejection rollers 16 and 17, at least one of which, in the example shown, is Ejection roller 17, with the rotary drive of the franking machine is coupled. The letter is then on the right in Figure 1 End of the transport route 13 issued.

Through the printing area of the thermal print head 10 is a Carrier tape 18 passed through, which, as known per se, made of a material with a defined electrical resistance consists or coated with such a material can be and in a meltable by exposure to heat Binder carries color particles. These become more selective Heating of the carrier tape 18 by the printing electrodes of the thermal print head 10 in a corresponding pictorial Transfer distribution from the carrier tape 18 to the letter, which then passes through the pressure area between the pressure rollers 11 and the platen roller 12 moves. The carrier tape 18 is delivered from a tape unwinding reel 19 and by one Tape drive roller 20 and a counter pressure roller 21 passed around. The tape drive roller 20 is with the drive of the Postage meter coupled and pulls the carrier tape 18 from the tape unwind spool 19. Is the tape supply of the tape unwinder 19 exhausted, the carrier tape 18 has the 22 dash-dotted line.

After the counter-pressure roller 21, the carrier tape 18 is one Guide pin 23 passed around the function of a collecting electrode has, and then comes in almost horizontal Course in the print area of the thermal print head 10. The Guide pin 23 connects the carrier tape 18 to ground potential and thus causes a current discharge from the carrier tape 18 by mass. The current becomes the carrier tape 18 supplied via the printing electrodes of the thermal print head 10, why this with a control circuit, not shown in Figure 1 which is known per se and which Pressure sequence or the selective control of the pressure electrodes of the thermal print head 10 controls.

The carrier tape 18 has a width of the thermal print head 10 corresponding width (see Figure 3), so that it is between the pressure rollers 11 passes through. It gets out of the print area led out and then reaches deflection elements 24, which are used as guide pins or as idling rollers can be executed. From there it becomes a tape take-up reel 25 supplied, that shown in Figure 1 Arrow direction is turned counterclockwise and the carrier tape 18 is wound up until it is filled. Then has the carrier tape 18 the course shown at 25.

In Figure 1 it can be seen that the thermal print head 20 on the carrier tape 18 acts on the top thereof, and that the letter to be printed under the carrier tape 18 by the Printing area must run, then the color particles in pictorial distribution of the carrier tape 18 transferred to it become.

In Figure 2 is shown in a longitudinal section how that Principle of a movable, independent of pressure elements Storage of a thermal print head at a franking machine can be realized. This is used for the pressure rollers 31 and the thermal print head 30 common carrier which the thermal print head 30 is movably mounted and the in turn be moved by a letter to be printed can. This carrier has the shape of a rocker 36, the trained in the manner of an angle lever and on one Swivel axis 37 in the device frame, not shown, stationary is pivotally mounted. The swivel movement takes place so that the horizontal part of the rocker in Figure 2 36 moved up or down relative to the transport path 33. This movement is generated by a letter, the one on the left side of the arrangement shown in the Arrow direction between two feed tractor assemblies 34 lifts according to its thickness, causing the end 36a on the lower axis 34a of the feed tractor assembly 34 resting rocker 36 raised by the letter thickness becomes. So that the pressure rollers 31, of which in Figure 2 shows only one, relative to the counter-pressure roller 32 raised because they are on the swing arm 36 stored, as can be seen better by Figure 3.

Deflection elements 43 and 44 are also on the rocker 36 provided for a carrier tape which in the direction of the arrow from a Supply roll, not shown, and supplied to a also not shown winding roll removed becomes. On the horizontal part of the rocker 36 is at 40 pivotably a holding device 39 for the thermal print head 30 stored. This holding device 39 consists of two Angle levers, only one of which can be seen in FIG. 2. This is at its end facing away from the thermal print head 30 coupled to the armature 46 of an electromagnet 45 at 47. The electromagnet 45 is on the downward Part 36 b of the rocker 36 attached.

The rocker 36 is thus by its weight with its horizontal Part or the pressure rollers 31 in the direction of the Counter-pressure roller 32 pivoted towards it, which in FIG left end 36a of the horizontal part of the rocker 36 of the lower axis 34a of the feed tractor arrangement 34. If this is introduced by one from the left Letter is raised, so will the horizontal part of the Swing arm 36 raised, whereby a height adjustment of the Thermal print head 30 is reached over the letter and the Pressure rollers 31 a predetermined pressure force on the Exercise imported letter if it is over the platen roller 32 moves.

Preferably at the moment the front edge of the Briefes on the counter-pressure roller 32 actuates the control the franking machine the electromagnet 45, so that the Thermal print head 30 supporting angle lever 39 in the counterclockwise direction (Figure 2) are pivoted and the thermal print head 30 lowered against the carrier tape 38 in its operating position becomes. The thermal printhead 30 is in this position and the electromagnet 45 shown in Figure 2. Then is after the letter has passed through the printing area of the Printing process ended, the thermal printhead 30 through Turn off the electromagnet 45 and extend its armature 46 back into its rest position from the carrier tape 38 be lifted off.

Figure 2 shows that depending on the dimensions of the used parts as well as when moving through the Adjustment paths dependent on leverage on the one hand Force of the pressure rollers 31 on a located in the transport nip Letter, on the other hand the pressure of the thermal print head 30 individually dimensioned on the carrier tape 38 can be.

A rocker arrangement is shown overall in FIG. 3, which comprises the device shown in Figure 2. The perspective representation applies to a viewing direction of the back of the arrangement shown in Figure 2 ago. The rocker 36 is with a support frame 36c for the pressure rollers 31 and the thermal print head 30. At the Swing arm 36 is a bearing 48 for the right pressure roller 31 recognizable. The left pressure roller 31 is likewise stored in the opposite part of the support frame 36c. In addition, the bearing axis 40 for the two angle levers 39 to recognize, to which the thermal print head 30 is attached is. The rocker 36 lies with its right one in FIG. 3 and tapered end 36a on the lower axis 34a of the upper feed tractor assembly 34, which consists of two on rollers guided tractor belts. These tractor belts are the tractor belts of the lower feed tractor arrangement 35 opposite.

A franking machine is shown schematically in FIGS shown in four different operating positions. The mode of operation is similar to that in FIG. 2 and 3 arrangement shown, but with a common carrier not for the thermal print head and the pressure rollers Spring force is applied, but by its own weight the pressure of the pressure rollers on one to be printed Letter determined. A carrier tape for color particles is in Figures 4 to 7 not shown.

FIG. 4 shows two feed tractor arrangements on the left part of the franking machine 54 and 55, between the one to be printed Letter 53 inserted in the direction of the arrow shown can be. The thermal print head 50 is on one Carrier board 59 attached, which in turn on a rocker 56 vertically slidably mounted in slot guides 58 is. The rocker 56 is at 57 on the device frame pivoted and lies with her left in Figure 4 End 56a on the lower axis 54a of the feed tractor assembly 54, so that it is raised by this when the Letter 53 between the two feed tractor assemblies 54 and 55 is drafted.

There are also ejection tractor assemblies at the right end of the letter transport path 61 and 62 shown. The upper Ejection tractor assembly 61 is with its upper axis 61a mounted on the rocker 56 and lies with its lower Part 61b on a letter 53, as soon as this after the Printing process output from the franking machine on the right becomes.

The print head 50 lies with its print bar in the print area between pressure rollers 51 and a counter pressure roller 52. The arrangement of these parts corresponds to that in the figures 2 and 3 shown. On an upper board part 60 the Swing arm 56 is an electromagnet 65 which is attached its anchor 66 connected to the joint point of a knee joint 67 is. This is at its upper end 68 on the Board part 60 stored and at its lower end with a Elongated hole on a pin 69, which on the carrier board 59 is attached. The lower part of the knee joint 67 is provided with a compression spring 70 which between the Hinge point and the pin 69 acts.

The pressure rollers 51 are on one in FIGS. 4 to 7 not visible lower projection of the rocker 56 mounted. Figure 5 shows the device shown in Figure 4 in one Operating state in which the letter 53 to be printed between feed tractor assemblies 54 and 55 are conveyed is. The rocker 56 is by lifting its left end 56a pivoted upward about the pivot axis 57, so that the Pressure rollers 51 are at a distance from counter-pressure roller 52, which is less than the letter thickness, which means that later The letter 53 arrives at this point Swing arm 56 is raised further and then by its own weight a predetermined pressure force across the pressure rollers 51 and exercises the letter 53 on the platen roller 52. The thermal print head 50 is then preset at the same time.

Figure 6 shows the operating state in which the letter 53 with its front edge between the pressure rollers 51 and Back pressure roller 52 has arrived. This is the swing arm 56 raised further and the thermal print head 50 preset. At this moment, the electromagnet 65 should be actuated to the thermal print head 50 in the printing area move.

FIG. 7 shows this operating state. The electromagnet 65 has tightened its anchor 66 and thereby the knee joint 67 stretched. This made the carrier board 59 with the Compression spring 70 pushed down so that the thermal print head 50 now on the carrier tape, not shown, in the printing area is present and on the letter 53 a predetermined print image applies. He practices on the carrier tape or the letter 53 a pressure generated by the force of the compression spring 70 is determined. The letter 53 is between the pressure rollers 51 and the platen roller 52 transported until it is output on the right side of the device.

Figure 8 shows a franking machine in which the thermal print head 80 on a carrier 86 for a pressure roller 81 is held, which is real to a counter-pressure roller 82nd can be moved linearly and in two stationary Guides 83 is guided. The movement of the wearer will caused by a feed tractor assembly 84 which is raised by a letter, not shown, if this between them and a lower feed tractor assembly 85 arrives. The feed tractor assembly 84 is at one Angle lever 87 mounted, the fixed pivotally mounted is. The upper leg of the angle lever 87 in FIG. 8 is via a rail 90 with the upper leg of another coupled pivotally mounted angle lever 91, whose shape and size corresponds to that of the angle lever 87. If the angle lever 87 is pivoted counterclockwise, so the angle lever 91 performs a similar Pivotal movement and thereby lifts the carrier 86 with one Pin 92 as far as the thickness of the between the Feeder tractor arrangements located letter corresponds. Thereby, the thermal print head 80 is set to a corresponding one Preset height.

The thermal print head 80 is on the carrier 86 with a carrier board 89 kept moving up and down can be and with slot guides 88 on pins of the carrier 86 is guided. The carrier board 89 has one sloping upper edge 93 on which the horizontally displaceable Armature 96 of an electromagnet 95 guided with a roller 94 is. The lower edge 97 of the carrier board 89 rests a spring 98 by which it is pressed up and which is supported with its lower end on the carrier 86.

When the solenoid 95 is turned on, it moves its anchor 96 to the left and presses the carrier board 89 their sloping upper edge 93 downward, so that the thermal print head 80 thereby from its preset position in the final operating position, as with the exemplary embodiments described above is the case. The type of drive shown in Figure 8 for the carrier board 89 can also be used for the carrier board 59 of the in FIG to 7 shown embodiment may be provided.

In Figure 9, an embodiment is outlined in which the carrier 86 as in the example according to FIG. 8 in its Height relative to a counter-pressure roller, not shown is linearly displaceable. The carrier 86 with the thermal print head 80 is arranged on a column 100 which is slidable is stored in fixed bearings 102. Around column 100 is a clamping band 104 looped by an electromagnet 106 to an idle state in which there is the column 100 loosely wrapped around, and a clamped state can be controlled in which it is the column 100 in the currently located Location jammed. If a postal item 53 the feed tractor assemblies 84, 85 is fed, so the upper Feed tractor assembly 84 according to the thickness of the mail 53 raised. The height movement is via a connecting arm 108 transferred to the carrier 86, which when released Clamping band 104 moves column 100 in bearings 102, so that the thermal print head 80 is a preset height relative to the counter-pressure element (not shown).

In this position, the electromagnet 106 is actuated so that the clamping band 104 locks the column 100. During the passing the mail item on thermal print head 80 remains Carrier 86 in the locked position. In this embodiment can be increased on the mail item 53 for printing Compressive force are applied without being between the counter-pressure element and the carrier 86 develops a relative movement. This embodiment is particularly in connection used with the ETR method where relative high pressure forces are required.

In the following examples, a portable back pressure element described, which is arranged with a stationary Thermal print head interacts. In Figure 10 the ETR thermal print head 110 arranged in a fixed position has a print bar 112, which is equipped with printing electrodes, which against an ETR carrier tape provided with a resistance layer Press 114. The pressure bar 112 presses indirectly against a counter-pressure roller 116 which rotates on rollers 118 is stored. The rollers 118 are angularly spaced held apart by a fork 120, which over a elastic holding element 122 with an adjusting device 124 connected is. The holding element 122 has two in one another slidable cylinder surfaces 126a, 126b, which is a coil spring Record 128. The holding member 122 causes the upper lateral surface of the counter-pressure roller 116 in the direction perpendicular to the printing surface or the pressure bar 112 of the Thermal print head 110 is resilient and one exerts predetermined pressure on the printing surface at 112. The Actuator 124 has two positions: in an advanced position Operating position presses the counter-pressure roller 116 against the mail item transported in the direction of arrow 117 (not shown); in a withdrawn rest position is the platen roller 116 from the pressure bar 112 of the Thermal print head 110 removed.

In the right part of the figure 10 there are further details the device in a partially sectioned side view recognizable. The platen roller 116 is on one Shaft 130 mounted, the axis of rotation 131 arranged stationary is. The shaft 130 is not on one side by one shown transport motor driven. The counter pressure roller 116 has an outer jacket 116a made of rubber, which with a hollow cylinder 116b made of aluminum. she is at both ends with the shaft 130 through a bellows 132 rotatably connected, of which in FIG. 10 only the left part is visible. The bellows 132 is through one elastic ring 134 attached to one end of the bellows in an annular recess 136 of the hollow cylinder 116b presses. The bellows 132 on the shaft 130 is through Adhesive or other connecting means connected. Another Possibility of connection is the shaft 130 in the area of the bellows 132 with polygonal surfaces, where the end of the bellows 132 is form-fitting is present.

Two impellers 138 are also arranged on the shaft in a rotationally fixed manner, the same outside diameter as the backing roller 116 have. The impellers 138 have an outer ring 138a made of rubber and a core ring 138b made of aluminum, the is attached to the shaft 130. In every tread of the Impellers 138 have a groove 140 in them. Every wheel 138 is a friction spring 142 opposite as a pressure element arranged, for reasons of clarity in the left Image part of Figure 10 have been omitted. The friction springs 142 have elevations 144 that are in line with the grooves 140 work together.

The fork 120 carrying the rollers 118 is with the holding element 122 connected by a hinge 146 whose axis of rotation 148 approximately perpendicular to the longitudinal axis 131 of the shaft 130 and approximately parallel to the direction of transport of the mail runs. The counter-pressure roller 116 can thus pivot movements Execute around the axis of rotation 148.

When the franking machine is in operation, the shaft 130 becomes Transport of the postal matter by the transport motor (not shown) driven. The impellers 138 and the platen roller 116 record the mail and carry it under Friction by the between the transport wheels 138, Counter pressure roller 116, friction springs 142 and thermal print head 110 formed transport gap. If the mail a part that bulges its surface, e.g. a staple or contains a coin, it takes on the postage contact surface of the counter-pressure roller 116 in one the pressure bar 112 and the shaft 130 containing Plane tilted about the axis of rotation 148 one that allows an even pressure on the postal matter in the direction perpendicular to the transport direction is exerted along the pressure bar 112. The pressure electrodes of the thermal print head 110 thus always remain in contact with the ETR carrier tape 114, which in turn is in contact with the surface of the mail item. This allows Color particles from the carrier tape 114 even on an uneven surface of the postal items are transferred evenly. The of the counter pressure roller 116 is generated by the coil spring 122 is set by the actuator 124 in an upward direction in FIG. 10 is pressed. After printing and run of the postal matter, the actuating device 124 is in its rest position moves, in which the pressure roller 116 a distance from thermal print head 110.

By using the bellows 132 and the bearing of the mantes 116a on the rollers 118 can one of the spring 128 of the holding element 122 caused lifting movement the lateral surface of the counterpressure roller which is in contact with the postal matter 116 are transmitted without the shaft axis 131 shifted. Also swiveling movements of this lateral surface the axis of rotation 148 are without displacement of the shaft axis 131 possible. The lateral surface facing the postal item nestles So elastic on the surface, so that also If the surface is uneven, even pressure is created becomes. In practice, the stroke movement of the lateral surface is up to approx. 3 mm.

FIG. 11 shows an embodiment of the adjusting device 124 detailed. An electromagnet 150 actuates a lever 152, the end of which is about a fixed pivot bearing 154 is rotatable. The holding element shown schematically 122 is moved up and down by lever 152. The Illustration according to FIG. 11 shows that the shaft 130 is arranged stationary. The one facing away from the postal service The outer surface of the counter-pressure roller 116 is covered by the rollers 118 stored. Due to the chosen arrangement, a Movement of the fork 120 in the direction of the mail Mantle surface of the counter-pressure roller 116 and thus the contact surface be moved up and down without the Wave 130 must be moved. The shaft 130 can therefore be a Assume an eccentric position with the counter-pressure roller 116. Thereby the overall result is a stable arrangement, the yet is highly agile and adequate Has rigidity to be able to transmit pressure forces.

In Figure 12, the lever 152 has a tooth area at one end 156, which is in engagement with a gear 158. At a rotation of the gear 158, for example, by a motor is driven, the lever 152 leads up and Movements and thus allows movement in addition to the above operating positions also a setting the pressure of the counter-pressure roller 116 on the mail.

Figure 13 shows an arrangement with the distance of the counter-pressure roller 116 from the print bar 112 of the thermal print head 110 depending on the thickness of a mail item can be. The backing roller 116 Actuator 124 is attached to a plate 160, the opposite of one attached to the housing of the franking machine Base plate 162 is displaceable by a spindle drive 164 is stored. The by an engine (not shown) driven spindle drive 164 has a spindle 168 attached to an arm 170 of plate 160. By operating the motor, the arm 170 and thus the Back pressure roller 116 together with the actuator 124 in directions indicated by arrows 166 relative to the base plate 162 adjusted. On the arm 170 is one by one Axis of rotation 172 rotatably mounted tractor assembly 174, which in the direction of arrows 175 swivel movements can perform. The swivel movements are over a Transfer arm 178 to a switch 180, the upon deflection of the tractor assembly 174 by a predetermined one Path, for example 3 mm, generates a switching signal. This switching signal is the motor of the spindle drive 164 fed, which adjusts the spindle 168 so long until the switching signal is no longer available.

The lower tractor assembly 174 is an upper, stationary Tractor assembly 176 arranged opposite, which with its transport path and the pressure bar 112 of the thermal print head 110 forms a transport plane 182.

When operating the franking machine, the tractor arrangements 176, 174 a postal item fed. Depending on the thickness of the mail the lower tractor assembly 174 is pivoted downwards, the link arm 178 closing the Switch 180 causes. The switching signal of switch 180 causes an adjustment of the spindle 168 and thus the Plate 160 in a direction that is the distance between the Contact surface of the counter-pressure roller 116 and the pressure bar 112 enlarged. In a through the rest position of the tractor arrangement The switch opens in the defined position 180 again and the switching signal drops. The engine of the Spindle assembly 168 is stopped and plate 160 has a position in which the platen roller 116 approximately on the The thickness of the mail item is preset. When transporting the Postal goods along the transport level 182 will be through the Counter-pressure roller 116 directly against the pressure bar 112 pressed, the counter-pressure roller 116 corresponding to the Execute bumps in the mail item can. Due to the presetting of the back pressure roller 116 their deflection movements remain on the thickness of the mail within a narrow range so that it comes close to constant force is pressed against the mail.

Numerous modifications are within the scope of the present invention and combinations possible. So it can in the Figure 10 shown arrangement with a movable counter-pressure roller 116 can also be combined with an arrangement which is shown in Figure 8 is shown and a movable thermal print head 80 preset to the thickness of the mail. The in Figure 8 shown thermal print head 80 can be in one variant can also be arranged in a stationary manner on the carrier 86.

It is also possible to use the presetting device shown in FIG instead of a spindle drive with a Equip clamping device according to Figure 9. Vice versa can by the tractor assembly 174 and switch 180 formed sensor arrangement for scanning the thickness of the mail item and setting a distance between the thermal print head and counter pressure element by a spindle drive too can be used in a device according to FIG.

Claims (19)

1. Franking machine having an electrothermal printing device with which postage stamps and/or image prints are printed onto postal goods, which are guided past it at a predetermined speed, by transferring ink particles in a distributed manner image-wise from a carrier band (114), which is heated by means of a thermoprinting head (110) in accordance with the imagewise distribution and at the same time is guided past the printing device, wherein a counter-printing element (116) is located opposite the thermoprinting head (110), with a counter-printing roller (116), which can be moved in a perpendicular direction in relation to the printing surface, being provided as the counter-printing element,

   wherein the counter-printing roller (116) can be adjusted along an axis, which extends so as to be perpendicular to the direction of transportation of the postal goods, by means of an adjusting device (124), which

   can adjust the counter-printing roller (116) and move it into an operating position, in which the counter-printing roller (116) presses against the postal goods under spring pressure, and into a rest position in which the counter-printing roller (116) is remote from the thermoprinting head (110),

   characterised in that the counter-printing roller (116) is flexibly mounted on a shaft (130), which is arranged parallel to the printing strip (112) of the thermoprinting head (110), in such a way that its surface of contact with the postal goods can be at different angles in relation to the printing strip (112) in a plane containing the printing strip (112) and the shaft (130),
   and in that the counter-printing roller (116) and also a drive (20) for the carrier band (114) are coupled with a rotary drive of the franking machine, with the postal goods being transported forwards at the predetermined speed in the printing range by means of the counter-printing roller (116).
2. Franking machine according to claim 1, characterised in that the thermoprinting head (110) is arranged in a stationary manner.
3. Franking machine according to claim 1, or 2, characterised in that at its ends the counter-printing roller (116) is connected to the shaft (130) in a fixed manner with respect to rotation by means of a resilient arrangement (132).
4. Franking machine according to one of the preceding claims, characterised in that provided as a resilient arrangement there is a bellows (132) which preferably consists of elastic material, for example of rubber or plastics material.
5. Franking machine according to one of the preceding claims, characterised in that the counter-printing roller (116) is mounted on a fork (120) which is connected to a holding element (122), preferably by means of a swivel joint (146), the axis of rotation (148) of which extends so as to be at least substantially perpendicular to the longitudinal axis of the shaft (130) of the counter-printing roller (116) and at least substantially parallel to the direction of transportation of the postal goods.
6. Franking machine according to claim 5, characterised in that the fork (120) has at least two rollers (118), which at an angular distance from each other on the peripheral side rotatably mount the counter-printing roller (116) on the side that is remote from the thermoprinting head (110).
7. Franking machine according to claim 5 or 6, characterised in that the holding element (122) contains an elastic portion, preferably a spiral spring (128) which can be deformed in a direction that is perpendicular to the printing strip (112) of the thermoprinting head (110), the shaft axis (131) of the shaft (130) preferably being arranged in a stationary manner.
8. Franking machine according to one of the preceding claims, characterised in that a lifting magnet is provided as the adjusting device (124).
9. Franking machine according to one of the preceding claims, characterised in that a lever arrangement (152, 154), which can be actuated by an electromagnet (150), is provided as the adjusting device (124).
10. Franking machine according to one of the preceding claims, characterised in that the adjusting device (124) comprises a toothed region (156) which can be displaced by means of a driven toothed wheel (158).
11. Franking machine according to one of the preceding claims, characterised in that at a distance from each other two running wheels (138), between which the counter-printing roller (116) is arranged, are connected to the shaft (130) of the counter-printing roller (116) in a fixed manner with respect to rotation.
12. Franking machine according to claim 11, characterised in that arranged as a pressure element opposite each running wheel (138) there is a frictional spring (142) that exerts a predetermined pressure on the running wheel (138).
13. Franking machine according to claim 11 or 12, characterised in that running wheels (138) and counter-printing roller (116) have the same diameters.
14. Franking machine according to one of the preceding claims, characterised in that a pre-adjusting device (174, 164, 160) is provided that adjusts the counter-printing roller (116) and moves it to a distance from the printing strip (112) of the thermoprinting head (110) as a function of the thickness of the postal goods.
15. Franking machine according to claim 14, characterised in that the thickness of the postal goods on the transportation path to the thermoprinting head (110) is scanned by a sensor (174, 178, 180) which, when a given thickness is exceeded, emits a signal for the purpose of controlling a positioning motor that adjusts the pre-adjusting device (160, 164, 174).
16. Franking machine according to one of claims 14 or 15, characterised in that the counter-printing roller (116) is arranged on a carrier (160) which contains a transporting device (174) for feeding in the postal goods, and in that the carrier (160) is adjusted by the pre-adjusting device (160, 164, 174).
17. Franking machine according to claim 16, characterised in that the transporting device (174) has a guiding wheel which can be moved in opposition to spring pressure and which in the event of a deflection by a given distance actuates a switch (180) which generates the signal.
18. Franking machine according to one of claims 14 to 17, characterised in that the pre-adjusting device contains a spindle drive (164).
19. Franking machine according to one of the preceding claims, characterised in that arranged on both sides of the thermoprinting head (10, 30, 50, 80) there are pressure elements (11, 31, 51, 81), the transportation gaps of which, formed with the counter-printing element (12, 32, 52, 82), lie in the respective plane that contains the printing strip of the thermoprinting head (10, 30, 50, 80) and is perpendicular to the transportation path of the postal goods (53) and which exert a pre-determined pressure on the postal goods (53) or the counter-printing element (12, 32, 52, 82) respectively and in that the thermoprinting head (10, 30, 50, 80) rests against the carrier band (18, 38) in a movable manner.

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