Printing device

The printing device comprises a print head unit, a transporting device for the printing material and a structural housing board on which the print head unit and the transporting device are mounted at one end in cantilevered manner and in a predetermined relationship relative to one another. The transporting device comprises a stiff support member which is rigidly connected to the housing board, a mounting member which extends substantially parallel relative to the housing board and is held on the stiff support member, and at least one transport roller for the transportation of the strip of printing material which is mounted at both ends. The stiff support member comprises connecting elements for releasably fixing th mounting member and also guide elements which co-operate with corresponding guide elements of the mounting member for exactly positioning the arrangement with reference to the support member. The first end of the transport roller is mounted at the housing board side and is releasably connected to a drive device and the second end of the transport roller is releasably mounted at the mounting member side.

The present disclosure relates to the subject matter disclosed in German application No. 100 21 038.4 of May 2, 2000, which is incorporated herein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a printing device for printing on printing material in the form of a roll, especially rolls of labels and/or receipts, including a print head unit and a transporting device for the printing material.

The purpose of the printing device incorporating the transporting device for the printing material (which is also referred to hereinafter as a roll printer or printer) is to wind off a strip of receipts or a strip of labels or the like from a roll, these receipts or labels that are to be printed upon being made of paper or synthetic material, to transport the strip through the roll printer and then, following the printing process, to eject the printed strip of printing material that is now in the form of a printed document from the printer for manual or automatic removal. In dependency on the nature of the document that is to be printed, there are different types of rolls which impose differing demands on the transporting device for the printing material during the transportation thereof through the printer. The present invention is mainly concerned with three different types of rolls which can be processed by the device in accordance with the invention:Receipt or label rolls comprising a running, non-adhesive strip of printing material.Self-adhesive label rolls comprising a backing strip, wherein the labels are stuck to a backing strip and are separated from one another.Self-adhesive label rolls without a backing strip, so-called “linerless” label rolls, comprising a running, adhesive strip of printing material.

In the case of all three types of strips of material, the functional elements of the printing device that come into contact with the strip of printing material during the transportation process, especially the print head, the transport rollers, including the print roller, the stripping edge and the drawing off roller, are subjected to heavy soiling from abraded paper and residual remnants of the adhesive. Consequently, for functional reasons, it is necessary to clean these parts at relatively short intervals. Moreover, these parts are also subject to wear so that replacement thereof is necessary after a certain service life.

A printer is known from WO 98/34791 AI, wherein a thermal print head together with a rigidly attached fixing member forms a unit which is held in position by means of a permanent magnet. Replacement of the print head in the event of failure or for cleaning purposes cannot be effected without loosening screws, i.e. it cannot be dismantled without tools.

In addition, the transport rollers for the printing material and the drawing off edge cannot be dismantled without tools and must be adjusted thereafter, and they can only be accessed with difficulty for cleaning purposes.

A pressure roller is known from U.S. Pat. No. 4,900,175, wherein the hollow axle thereof is provided with recesses and a groove at one side. This is inserted in the axial direction into a matching central boring of a drive wheel where it is a snug-fit, and it latches therein in the functional position. The pressure roller can easily be dismantled in the axial direction by releasing the latch.

A printer having an easily dismantled print roller is known from DE 40 04 930 AI. The print roller, which is mounted at each end in the printer frame, can be removed from the printer perpendicular to the axis of the pressure roller after actuating two release buttons. The problem here, however, is that in the case of this construction, replacement of the printing material or a fresh insertion thereof causes difficulties and is an extremely laborious process.

The important thing for this purpose is a freely accessible, open side for the insertion of the strip of printing material.

SUMMARY OF THE INVENTION

The object of the present invention is to enable the parts of the transporting device coming into contact with the strip of printing material to be easily replaced from the freely accessible insertion side of the strip, without requiring subsequent adjustments.

In accordance with the invention, this object is achieved by a printing device for printing on printing material in the form of a roll, especially label and/or receipt rolls, includinga print head unit,a transporting device for the printing material,a housing board, on which the print head unit and the transporting device are held at one end in cantilevered manner and in a predetermined relationship relative to one another,wherein the transporting device comprises a stiff support member which is rigidly connected to the housing board, a mounting member which extends substantially parallel relative to the housing board and is held on the stiff support member, and at least one transport roller for the transportation of the printing material which is mounted at both ends,wherein the stiff support member comprises connecting elements for releasably fixing the mounting member and also guide elements which co-operate with corresponding guide elements of the mounting member for exactly positioning the arrangement with reference to the support member, and wherein the first end of the transport roller is mounted at the housing board side and is releasably connected to a drive device and the second end of the transport roller is releasably mounted at the mounting member side.

A particularly easy to implement and thereby functionally excellent design for the guide elements of the mounting member and those of the stiff support member is provided in the form of studs and mutually matching borings. The studs may be provided selectively on the support member or on the mounting member or else on the support member and the mounting member, whereby the mounting member or the support member then comprises the borings matching the studs.

The mounting member may be rod-like or plate-like.

A particularly preferred embodiment of the mounting member is provided by a plug-in guide member which is displaceably guided in snug-fitting manner on the stiff support member perpendicularly relative to the plane of the housing board. Preferably, the guide means on the support member is designed in such a manner that the plug-in guide member can be displaced from a first operational position into a second non-operational position in which the plug-in guide member is still held on the support member, but the transport roller is freed for servicing/replacement.

The guide means of the plug-in guide member may, in principle, form the guide element for the support member and the section of the plug-in guide member sliding in the guide means may form the complementary guide element of the mounting member.

However, it is simpler for the purposes of manipulation and manufacture if the guide means of the plug-in guide member is produced with greater tolerances and if special guide elements are provided for the exact positioning process, especially in the form of the previously described studs and the mutually matching borings.

The mounting of the transport roller can, in principle, be such that the ends of the transport roller comprise bush bearings in which the bearing journals at the housing board and the mounting member sides engage. However, due to the fact that the transport roller represents a part subject to wear, this is preferably provided with bearing journals at the ends thereof so that they can then be inserted into bush bearings at the housing board and the mounting member sides.

Preferably, the mounting member, especially too in the form of the plug-in guide member, is fixed in the operational position by means of a latch formed on the stiff support member. Release of this latch enables the mounting member to be released and removed from the operational position in a particularly simple manner.

The plug-in guide member (or more generally, the mounting member) that is adapted to be released and removed by means of a handle enables, in advantageous manner, the transport roller and all of the parts of the transporting device coming into contact with the strip of printing material to be easily removed from the printer without the use of tools for the purposes of cleaning or replacement. A further advantage is that the dismantling and assembly of the parts requiring cleaning can be effected from the same side of the printer as is used for the insertion of the roll incorporating the strip of printing material that is to be printed.

This side of the printer, which is generally completely surrounded by a printer housing, must, in any case, be accessible via a housing door or flap for the purposes of inserting the receipt or label rolls. Consequently, no other housing parts need to be dismantled in order to dismantle the parts requiring cleaning.

With the aid of the printer design in accordance with the invention, each of the three types of label rolls or receipt rolls described hereinabove can be selectively processed on each occasion, namely with a thermal coating or, without a thermal coating in combination with a print ribbon unit or, where necessary, using other types of printing process, such as an e.g. inkjet process.

The replacement of the label or receipt roll by inserting the strip of printing material into the printer is effected in a very simple and user-friendly manner by means of a single actuation of a handle due to the cantilevered arrangement of the print head unit and the transporting device for the printing material on the housing board. If necessary, lifting of the thermal print head can thereby be simultaneously associated with a simultaneous pivoting action of a pivot roller.

The utilisation of an extruded profile as the stiff support member for the transporting device for the printing material is, in the embodiment thereof in accordance with the invention, a particularly advantageous and cost-effective solution. A plurality of functions can be implemented in a practical manner due to the extruded molding and the molded channels therein, such as for example, the mounting of the arrangement on the housing board, the guide-centralising process and the latching of the mounting member (and, if necessary, the guiding arrangement for the plug-in guide member) and hence, the mounting of the transportation pressure roller and the drawing off roller and the mounting of the stripping edge, the attachment and mounting of a light barrier for scanning the strip of printed material and the guiding arrangement for and the attachment of a deflector plate for the “linerless” label rolls.

Extremely good, uniform printing over the whole of the printing area is achieved by virtue of the stiffness of the extruded profile and an additional, single-sided adjustment of the lie of the print head should this need to be provided. This provides advantages, above all when printing on rolls of different widths.

The processing of rolls of differing widths is simplified still further by means of an additional adjustment of the drawing off roller. The effect is thereby achieved that, independently of the width of the roll, the edge of the strip of printing material facing the housing board will always run along the same stop member so that no adjustment will be necessary when inserting a roll of different width.

Mounting of the light barrier in a molded channel of the extruded profile in slideable manner has the advantage of allowing adjustment over at least half of the maximum width of the strip of printing material and hence the possibility of adapting the position of the light barrier to labels which are difficult to scan because their outer shape deviates from a rectangular shape. Thus, for example, round labels can be processed where, ideally, the scanning thereof should be effected at approximately the center of the diameter of the label.

Due to the construction of the universally employable transporting device for the printing material with its easily replaceable parts and groups of parts, there is also the advantage that it can easily be equipped or stripped when assembling the printer at the manufacturers or the users. Thus, for example, when using the printer as a simple receipt strip printer, the light barrier, the drawing off roller, the pivot roller and the wind-on roller may simply be left off although the basic concept remains the same, whilst it can subsequently be re-equipped if so desired.

As a result of the simple facility of inserting the strip of printing material laterally into the printer and the straight line path of the strip of printing material between the print head unit and the transportation unit without touching any parts, the printer is also suitable for processing “linerless” label rolls in an advantageous manner.

The only functional prerequisite is the need for a print roller having a non-stick surface coating, an additional deflector which prevents the adhesive strip of printing material from being wrapped around the transport/print roller and a non-stick coated deflector plate for covering the upper surface of the extruded profile.

Basically, these additional measures may be provided either on the printer, or they can be added later by simply replacing or installing the parts.

These and further advantages of the invention will be explained in greater detail hereinafter with the aid of the description and the drawings.

FIGS.1and also2A and2B show a printer1for printing on a rolled strip of labels or receipts—referred to hereinafter as a strip of printing material2—consisting of a transporting device3for the printing material and a print head unit4which are both secured at one end in cantilevered manner on the roller side5of a housing board6for the printer1. The housing board6forms a part of the printer housing which, for the purpose of simplifying the Figures, is not illustrated and encloses the printer1on all side in known manner, and which comprises a housing door or flap for the insertion of the label or receipt roll and also an outlet opening for the printing material after it has been printed upon.

The drive means7for the transporting device3for the printing material is arranged on the opposite, driver side8of the housing board6which is remote from the roller side5. The not illustrated control system for the printer is also preferably located on this driver side8which is not accessible to the operating personnel.

The print head unit4is constructed in accordance with the known state of the art and, in consequence, it will not be described in detail. A thermal print head10is pivotally mounted about a pivotal axis11on a stiff print head mounting9which is rigidly connected to the housing board6. The thermal print head10can be moved from an insertion position13for the printing material which is illustrated by full lines inFIGS. 2A and 2Binto a printing position14which is illustrated by dash-dotted lines by means of a handle12and an additional, not illustrated lever mechanism. Here, as is known, the lever mechanism executes a resilient over-throw action so that the printing line of the thermal print head10will rest on a print roller15of the transporting device3for the printing material under the influence of a corresponding spring force. The thermal heating elements16forming a printing line thereby lie, in known manner, in parallel with the print roller15on the surface of the strip of printing material2which is fed in the direction of the arrow17between the driven print roller15functioning as a transport roller and the stationary thermal print head10. The printable side18of the strip of printing material2facing the thermal print head10is provided with a thermo sensitive layer which is converted into another colour thereby producing a printed image as a result of the increase in temperature which occurs when the thermal heating elements16covering the whole width of the strip of printing material2are appropriately controlled.

As a departure from the so-called direct thermal printing process described above, the printer may also be used as a thermal transfer printer by adding a driven print ribbon. This printing process is likewise known in the state of the art. Consequently, the illustration of the print ribbon and the drive means therefore has been dispensed with. In the case of the thermal transfer printing technique, an additional print ribbon is moved in synchronism between the thermal print head10and the strip of printing material2and, by appropriate control of the thermal heating elements16, ink from the print ribbon is transferred to the surface of the strip of printing material2which does not comprise a thermo-sensitive layer in the case of this printing technique. Basically however, the design of the transporting device3for the printing material and the print head unit4remain the same when switching from direct thermal printing to thermal transfer printing.

The path of the clearly emphasised strip of printing material2,2′ or2″ through the printer1is illustrated inFIGS. 2A and 2Bin the insertion position13of the thermal print head10. This path varies however in dependence upon which of the three types of roll that have already been explained in connection with the description of the state of the art is to be printed upon and issued as a printed document.

a) Receipt or Label Rolls Having a Running, Non-adhesive Strip of Printing Material (FIG. 2B)

The strip of printing material2of a receipt or label roll21that is loosely mounted on a dispensing mandrel19and is fixed laterally by two stop members20is deflected over a guide roller22and then runs between the mutually spaced print head unit4and the transporting device3for the printing material whereafter it passes between the thermal print head10and the print roller15for printing purposes.

The driven print roller15transports the strip of printing material2further in the direction of the arrow17to a not illustrated outlet opening in the printer housing whereat the printed document is either separated manually at a knife edge or mechanically by means of a driven cutting device, or it is rewound onto a roll externally of the printer in an additional, not illustrated unit. These could also be self-adhesive labels that are stuck to a backing strip and exit from the printer in the form of complete strips and are only detached from the backing strip at a later time point.

b) Self-adhesive Label Rolls on a Backing Strip (FIG. 2A)

In known manner, the self-adhesive labels are adhered, either immediately adjacent to one another or mutually spaced, to the side of a backing strip23facing the thermal print head10. The labels, together with the backing strip23, form the strip of printing material2′ illustrated in FIG.2A. The path followed by this strip as far as the print roller15is identical to that of the roll of type a). However, immediately following the print roller15, the backing strip23is turned sharply round a stationary drawing off edge24. This causes the labels to be separated from the backing strip23and, following the stripping edge24, to be dispensed in the direction of the arrow17through a not illustrated outlet opening in the printer housing.

The drawing off force needed to strip off the labels is produced by means of a pair of rollers which are disposed after the drawing off edge24and consist of a driven drawing off roller25and a pivot roller26. The backing strip23is then wound up by means of a likewise driven winding mandrel27. In order to insert a new label roll21, the thermal print head10is pivoted into the insertion position13by means of a handle12. This movement of the handle12simultaneously causes, via a not illustrated lever mechanism, a pivot lever28having the pivot roller26mounted therein at one end to pivot away from the printing position depicted by dash-dotted lines inFIG. 2Ainto the insertion position illustrated by full lines in order to simplify the process of inserting the strip of labels2′. After it has been pivoted back into the functional position depicted by the dash-dotted lines, the pivot roller26causes wrapping of approximately 180° to occur around the driven drawing off roller25and hence slip-free transportation of the backing strip23. The pressure roller15and the drawing off roller25are provided with a resilient covering68of rubber or synthetic material for improving the transportation properties.

The “linerless” strip of labels2″ is wound onto the label roll21with the adhesive surface on the inside. The outer face18that is to be printed upon is provided, as is known, with an additional non-stick coating so as to easily enable the superimposed turns on the stock roll21to be released from one another. The path of the strip of labels2″ through the printer and the emission of the printed document is the same as for the roll of type a). The pressure roller15thus simultaneously forms the transport roller for the “linerless” strip of labels2″.

In contrast to a) however, the adhesive rear face of the “linerless” strip of labels2″ must be prevented from adhering to parts of the printer1during its passage therethrough. Consequently, additional, inherently known measures are necessary, such as a non-stick coating on the print roller15, an additional deflector on the print roller15for preventing the adhesive strip of labels2″ from being wrapped around it and a non-stick coating on every part which could come into contact with the adhesive side of the strip of labels2″.

The transporting device3for the printing material in accordance with the invention is illustrated in detail inFIGS. 3to5. The print roller15, which simultaneously forms a transport roller for the strip of printing material2,2′,2″, is mounted by means of its left-hand, first bearing journal29in the housing board6, said bearing journal29comprising a shaped portion differing from the circular shape, e.g. a key surface30which is insertable in snug-fitting, play-free manner into a matching central boring31in a drive wheel32thereby enabling the print roller15to rotate therewith in slip-free manner. The drive wheel32is connected to the drive motor7, e.g. via a not illustrated toothed belt.

In the same manner as for the print roller15, the drawing off roller25is mounted in the housing board6by means of a ball bearing59via its left-hand bearing journal33which is a snug-fit centrally of the drive wheel34so as to rotate therewith.

A stiff support member35, which is formed from an extruded profile of aluminium and comprises two dove-tailed grooves36at its lower end for accommodating a plug-in guide member37, is fixed perpendicularly relative to the housing board6between the print roller15and the drawing off roller25on the roller side5of the housing board6. The plug-in guide member37likewise comprises two projections38that match the grooves36and it is thereby displaceably mounted in the stiff support member35perpendicularly relative to the housing board6.

A leg39is bent up through 90° from the plug-in guide member37which is in the form of a sheet-like part, said leg being provided with two centralising borings40with which the plug-in guide member37is fixed on two centralising studs41when it is inserted into its functional position. The centralising studs41are pressed into molded channels42in the extruded profile35, which channels are in the form of segments of a circle.

A molded part of synthetic material44is fixed in a further dove-tailed molded channel43in the extruded profile35, there being formed on said molded part a resilient latch45which latches in a recess46in the leg39when the plug-in guide member37is inserted into its functional position. Two bush bearings47,48are attached to the leg39, said bushes being respectively aligned with the print roller15and the drawing off roller25and serving to accommodate the bearing for the right-hand bearing journal49of the print roller15and the right-hand bearing journal50of the drawing off roller25.

By pressing on the easily accessible resilient latch45, the plug-in guide member37can easily be released and removed in a direction perpendicular relative to the housing board6. Thereafter, the print roller15and the drawing off roller25can be removed in the same direction, e.g. for cleaning purposes or for replacement by a new roller.

In order to make the mounting of the rollers15and25even easier, respective pilot chamfers51are formed on the respective pairs of bearing journals29,49and33,50. The two projections38are also provided with pilot bevels52for easy insertion of the plug-in guide member37.

A radius-like shaped portion53is bent up from the plug-in guide member37below the print roller15, a straight end piece, the so-called stripping edge24, being formed at the edge of said shaped portion. Consequently, an additional part is not required for this stripping edge24which is needed for the purposes of detaching the self-adhesive labels from the backing strip. Due to the integration thereof in the plug-in guide member37, this is stiffened in an advantageous manner as a result of the radius-like shaped portion53. The insertion of the plug-in guide member37is thereby simplified and the stripping edge24is easy to clean when the plug-in guide member37has been removed.

An additional fine adjustment means is built into the bearing for the right-hand bearing journal49of the pressure roller15for adjusting the parallelism of the thermal print head10relative to the print roller15, as can best be seen fromFIGS. 4 and 5. The bush bearing47is fixed in the leg39of the plug-in guide member37in such a manner that it is secured axially by means of a locking washer54but is adapted to rotate in sluggish manner by virtue of an additional corrugated washer55that is clamped between the leg39and the locking washer54. An additional adjustment cam56, upon which the thermal print head10rests in the printing position, is formed on the bush bearing47. By rotating the bush bearing47and hence the very slowly rising adjustment cam56formed thereon, the parallelism of the thermal print head10and of the print roller15relative to one another can be adjusted and the results of the printing operation thereby optimised. The cam56thereby forms a stop member for the thermal print head10. This is particularly important when printing a narrow label roll and the strip of labels2′ (the strip of printing material) runs off-center relative to the thermal print head10in the vicinity of the housing board6. As a stop member, the cam56prevents the thermal print head10from tipping onto the right-hand side during the resilient setting thereof into the printing position14.

A further method of adjusting the transporting device3for the printing material is to be found in the bearing for the drawing off roller25. The right-hand bearing journal50is mounted in a bush bearing48that is fixed in the leg39of the plug-in guide member37, this bush bearing48, in like manner to the bush bearing47, being secured axially by means of a locking washer54and being adapted to rotate in sluggish manner by virtue of an additional corrugated washer55that is clamped between the leg39and the locking washer54. The bush bearing48has a neck collar58located eccentrically of the central boring so that the drawing off roller25will execute a slight pivotal movement about its left-hand bearing59in the housing board6, which bearing is in the form of a ball bearing, when the bush bearing48is turned. The pivoting of the central axis60of the drawing off roller25that is normally perpendicular to the housing board6affects the straight line path of the strip of printing material2′ and the backing strip23through the printer1. A backing strip stop member61is rigidly attached to the end of the plug-in guide member37facing the housing board6. The bush bearing48is now adjusted such that the edge of the backing strip23facing the housing board6tends towards the stop member61and presses lightly against it whilst it is running. It is thereby possible, in advantageous manner, to process self-adhesive label rolls of differing width that are disposed on a backing strip (rolls of the b. type) without adjusting the bush bearing48and without the need for a second backing strip stop member at the other edge of the backing strip.

During its passage through the printer, the strip of printing material2,2′ and2″ passes through a forked light barrier62which is used for scanning the labels on the backing strip23, or for scanning for printed forms which are already present on the stock roll21. The scanning signals are used by the printer control system, as is known, for synchronising the outer contours of the labels or the pre-existing printed forms with the printed image that is to be printed thereafter by the thermal print head10.

For the purposes of accommodating the forked light barrier62, a preferably hexagonal molded channel63is formed in the extruded profile35, a bush bearing64being pressed into the molded channel at the end face of the extruded profile35remote from the housing board6. A forked light barrier body65is mounted in slideable manner on the plate side of the extruded profile35in the molded channel63and partially projects through a break-through66in the plate6into the drive space8. The forked light barrier62can be adjusted transversely relative to the strip of printing material2,2′ or2″ over a large range of adjustment by means of a threaded spindle67which is mounted and axial secured in the bush bearing64and the housing board6. This is especially advantageous when self-adhesive labels that differ from a rectangular shape, e.g. round labels, are being processed whereby the scanning thereof should ideally be effected approximately centrally relative to the diameter of the labels.

For printing on self-adhesive labels without a backing strip (“linerless”), whence each of the parts coming into contact with the adhesive side of the label strip2″ should be coated in non-stick manner, the upper surface69of the extruded profile35must also be coated in non-stick manner, e.g. with PTFE. As an alternative solution to this, rather than a non-stick coating, the upper surface69could be covered by a not illustrated, additional deflector plate that is itself coated in non-stick manner. As was the case for the plug-in guide member37, two projections38may, for example, be formed on the deflector plate, said projections being matched to two molded channels70in the extruded profile35into which the deflector plate can be inserted and then secured between the housing board6and the leg39following the mounting of the plug-in guide member37.

The embodiment of the present invention that has been described merely serves as an illustration of the inventive concept and it also encompasses other alternative and equivalent embodiments which would be perceptible to the skilled person from a reading of the embodiment described, e.g. the implementation of a simple strip printer which dispenses with a light barrier, a stripping edge, a drawing off roller, a pivot roller and a wind-on roller.

In particular, it can be perceived from the preceding description, that the printing device in accordance with the invention may be constructed and equipped in such a manner that all of the currently available types of label can be processed by the same printing device without the need for modifications thereto. In like manner, it is apparent that a printing device that is initially designed for the printing of receipt rolls can be easily and cheaply converted for printing on “linerless” label rolls or can be added to the printer for backing strip type labels.