EP0505444B1 - Arrangement for the mechanical coupling of units of an electrophotographic printing or copying device - Google Patents

Abstract

The invention relates to an arrangement for the mechanical coupling of units, e.g. a printing mechanism (15) of an electrophotographic printing or copying device, with other units (23, 24) in axially parallel alignment with the conveyor path of a recording substrate (12). A basic unit (28), especially one containing the printing mechanism (15), is jointedly coupled via a cross-member (30), especially consisting of two individual cross-member components (301, 302), to a bearer (32) arranged vertically in relation to a device frame (1). In turn, the units (23 or 24) are linked in paired recesses (e.g. C1, C2) axially parallel in relation to the basic unit.

Description

The invention relates to an arrangement for the mechanical coupling of structural units, such as. B. a printing unit of an electrophotographic printer or a copier with other units in an axis-parallel orientation with respect to the transport path of a continuous recording medium.

Printers or copiers working according to the electrophotographic principle are generally known. The electrophotographic printing principle as such is relatively complex. A continuously revolving photoconductor drum is generally provided as an intermediate carrier for print information, which is initially charged evenly in its circulation in order to generate a latent charge image. The uniform charge is optically discharged point by point, depending on the pressure information, and a charge distribution corresponding to the pressure information is thus generated on the intermediate carrier. Using electrostatic forces, this charge image is colored by a toner mixture, then the toner particles are transferred to a recording medium and chemically or thermally fixed there.

Particularly critical in this process is the transfer of the toner particles onto the recording medium, the so-called printing, the further transport of the recording medium with the toner image which has not yet been wiped over, and the fixing process. Especially in this area of the transport path of the record carrier through the printer or the copier, the quality of the print result is decisively influenced. For example, it is essential that the recording medium in the transfer printing station be exactly parallel to the axis and without relative speed with respect to the intermediate carrier, ie the photoconductor drum is moved, otherwise the printed image is already blurred here. The fixing process is similarly critical, in particular when the fixing of the toner image on the recording medium is carried out by means of the thermal printing method. In this method, the recording medium runs between a pair of rollers, the so-called fixing roller or the pressure roller. The heated fixing roller, which faces the image side of the recording medium, emits a sufficient amount of heat to the recording medium in order to plasticize the toner particles in combination with the pressure exerted by the pressure roller and melt them onto the surface of the recording medium. Here, too, it is very important that the said pair of rollers of the fusing station is set exactly axially parallel to the transport path of the recording medium, otherwise not only mechanical crushing of the conveyed recording medium arises but also errors in the fixing, which lead to a reduction in the print quality.

It has to be made clear that today's electrophotographic printers, which generate the print information point by point using the raster process, already realize a raster of the order of 600 dpi (dots per inch) and more in the high-performance range. This corresponds to screen dot widths on the order of 0.04 mm and below. These figures illustrate the mechanical and structural requirements that must be placed on the accuracy of the transport of the record carrier in relation to the individual units of the electrophotographic printer or copier if one wants to maintain the contrast sharpness that can be achieved by the printing process in the print result.

Also known is the basic mechanical structure of such printing or copying machines, which operate on the electrophotographic principle. In addition to the exact assignment of the individual units of the printing or copying device to the transport path of the Record carrier must also be taken into account that individual units, for example for maintenance work, should be relatively inexpensive to access. Finally, at least some of these units should also be able to be pivoted away from the transport path of the record carrier. This applies in particular when the recording medium is in the form of continuous paper and the beginning of a paper web must first be inserted into the printer or copier before the start of a printing process.

The mechanics of electrophotographic printing or copying machines is accordingly complicated and time-consuming. For easier assembly, but also for reasons of maintenance technology, electrophotographic printing or copying devices are therefore constructed in a modular manner from individual structural units, with the corresponding tolerance limits being observed within a module, so that it is then relatively easy to replace, apart from a secondary condition, namely that, after such an exchange, the required axis-parallel assignment to the corresponding part of the transport path of the record carrier must again be established. The first assembly when assembling the individual structural units to form a printing or copying machine therefore usually requires a series of manual and time-consuming measures, especially in order to align all the individual structural units exactly parallel to one another. The same applies if inspection or maintenance work has to be carried out.

Based on the consideration that it must be possible to arrange the elements of these units to one another within individual integrated structural units such that they can be positioned in the individual module without particular effort, in particular in the case of wearing parts with regard to specific fixed points, the object of the present invention is to develop an arrangement of the type mentioned in such a way that with simple means during an initial assembly, but also when an exchange of individual structural units, an axis parallel is readily achieved Allocation of the individual units to one another can be realized without the need for complicated and time-consuming adjustment processes.

With an arrangement of the type mentioned, this object is achieved according to the invention by the features described in the characterizing part of patent claim 1.

Basically, the solution according to the invention is based on the fact that the electrophotographic process already specifies a printing unit as the core of such a printing or copying device, in the center of which the intermediate carrier, i. H. the photoconductor drum is arranged. As indicated at the outset, a plurality of individual assemblies are already arranged around the photoconductor drum, which must be assigned to them precisely in order to be able to generate a correct, colored charge image corresponding to the printing information. It therefore makes sense to design this core piece of an electrophotographic printing or copying device as a structural unit. Furthermore, it can be expedient to construct this printing unit as an integrated basic unit in connection with the devices which bring the recording medium to and from this printing unit and remove it again. As a unit, it can be designed in such a way that this approach and removal of the recording medium to the printing unit takes place exactly. H. that in particular the paper guide elements also allow a perfect, axially parallel transport of the recording medium with respect to the photoconductor drum. With such or a similar basic unit, however, the remaining structural units of the printing or copying device must now be coupled exactly axially parallel.

According to the invention, a support is provided for these components which are not integrated into the basic unit and which has corresponding receptacles for the components to be attached, so that these components are already exactly aligned with respect to the carrier by simple hanging. Then the problem arises of firstly aligning this carrier, in turn, parallel to the axis of the basic unit mentioned. This is achieved here by means of a crossbeam which is connected on the one hand to the basic unit in two articulation points and on the other hand to the support in a further two articulation points. If the base unit is fixed on a frame or frame of the printing or copying machine, then after the carrier has been coupled to the base unit via the cross member, it is only necessary to align it with respect to the frame in one direction, in particular the vertical, with the axis parallelism of the carrier is inevitably obtained with the basic unit and thus the structural units to be fixed on the carrier are in turn assigned to the basic unit in each case parallel to the axis without further adjustment measures.

It also follows from this that the individual structural units attached to the carrier are interchangeable, provided the suspension points of the structural units on the carrier are tolerated closely enough. As an example, this applies in particular to the fixing station of the printing or copying device, which is designed as a separate structural unit. In the introduction it was stated that their axis parallelism to the printing unit is particularly critical. In addition, the fixing station, if the thermal printing process is used for fixing, is also subject to thermal expansions during operation and therefore corresponding degrees of freedom for thermal expansions must be provided without the axis parallelism being lost. According to a further development of the invention, this can be achieved in that the fixing station is only suspended in side parts of the carrier, is axially fixed with respect to this carrier at a bearing point and rests on a further support point fixed to the housing. The fixing station for operation is thus articulated in both the axial and vertical directions with two degrees of freedom with respect to the rigid support, but is nevertheless easily replaceable as an individual structural unit.

Other developments of the invention result from the rest Subclaims and are explained in detail in the following description of an embodiment.

• Figur 1 in einer Prinzipdarstellung die Aufbaustruktur eines elektrofotografischen Druckers, bei dem diverse Baueinheiten bezüglich eines Transportweges eines bahnförmigen Aufzeichnungsträgers exakt auszurichten sind,
• Figur 2 und Figur 3 in einer Drauf- bzw. einer Seitenansicht die erfindungsgemäße, konstruktive Anordnung zum mechanischen Koppeln derartiger Baueinheiten, die eine achsenparallele Ausrichtung dieser vom Aufzeichnungsträger durchlaufenen Baueinheiten gestattet.

An embodiment of the invention is explained in more detail below with reference to the drawing, in which:

• FIG. 1 shows a basic illustration of the structure of an electrophotographic printer in which various structural units are to be precisely aligned with regard to a transport path of a web-shaped recording medium,
• Figure 2 and Figure 3 in a top view and a side view of the inventive design for mechanical coupling of such units, which allows an axis parallel alignment of these units passed through by the recording medium.

The electrophotographic printer shown schematically in FIG. 1 has a supply table 10 for receiving a supply stack 11 made of pre-folded continuous paper 12. The record carrier 12 is fed to the actual electrophotographic printing unit 15 via a paper dividing device 13 and a pivotable actuating rocker 14 provided with paper guide elements. This has a transfer station 17 which can be swiveled in and out of a photoconductor drum 16 and further devices which are arranged around the photoconductor drum and are required for the electrophotographic process.

Thus, the photoconductor drum for generating a toner image on the recording medium 11 is charged by a charging device 18 and discharged as a function of the print information via an LED character generator 19. The charge image generated is colored in a developer station 20 with a developer mixture of toner and carrier particles and transferred to the recording medium 12 in the transfer printing station 17. Thereafter, the photoconductor drum 16 is unloaded via an unloading station 21 and cleaned in a cleaning station 22, so that it can be recharged via the charging device 18.

From the transfer printing station 17, the recording medium 12, which is now carrying the toner image, is fed to a fixing station 23 for the wipe-proof fixing of the toner image and then placed on a deposit table 24. If the printer is coupled, for example, to other printing devices in order to, for. B. To enable front or back side printing, the web-shaped recording medium 12 can also be fed directly to the paper dividing device 13 via external paper feed channels 25. Furthermore, it is conceivable to use a supply stack 26 which is not integrated in the printer as a supply stack; further paper feed elements 27 may be necessary.

Even the schematic illustration illustrates the relatively complex structure of an electrophotographic printer, in which the printing result is also determined, among other things, by how precisely the path of the recording medium 12 through the individual stations is. Decisive for this are precise paper guides, in particular deflections, and in particular also the parallel arrangement of the structural units to be traversed by the recording medium.

Figure 1 illustrates even in the schematic structure that it is expedient to design at least the photoconductor drum 16 and the units 17 to 22 arranged around it as a common structural unit. Furthermore, all essential elements for guiding the recording medium 12, at least those in the area of the electrophotographic printing unit 15, are also to be understood as one structural unit. In this embodiment it is assumed that the elements for paper transport z. B. 13, 14 and 27 together with the electrophotographic printing unit 15 form a mechanically rigidly coupled unit, which is referred to below as the basic unit. As FIG. 1 shows, the fixing station 23 and in particular also the paper stacking devices, in particular the storage table 24, are spatially separated therefrom. There is therefore the problem of assigning these spatially separate structural units, such as the storage table 24 with its stacking devices and the fixing station 23, to the basic unit 28 parallel to the axis.

FIGS. 2 and 3 now show in a top and side view in detail the means by which this axis-parallel assignment is achieved without having to first set this parallelism during assembly by means of complicated adjustment measures. In order to clarify the solution according to the invention, all details which are not absolutely necessary are omitted from the illustration in FIGS. 2 and 3, so that a corresponding clarity of the illustration is achieved. Thus, only a frame element of the base unit 28 is indicated schematically in a partial section, it being assumed that all parts of the base unit 28 have a defined position in relation to this frame element. The base unit 28 has two bearing eyes 29, which are aligned parallel to one another as required. A cross member 30 is hooked into these bearing eyes 29 via connecting pins 31. This cross member 30 consists of two cross member elements 301 and 302, for example, which are designed as two cast rails and have no rigid connection with one another.

Another coupling element is a carrier 32, the basic shape of which is U-shaped, i. H. on a base part 321 there are two side parts 322 at a distance from one another and facing one another. The side parts 322 of the carrier 32 have arms 323 which are rigidly coupled to them and protrude laterally upwards, each with a further bearing eye 324, into which one of the ends of the cross member elements 301 and 302, respectively, of the basic unit 28.

The carrier 32 is connected via three support points 325 and 326 via its base part 321 to a framework 1 of the printer, which is only shown schematically. The carrier 32 is aligned exactly vertically to the printer frame 1 via these three support points 325 and 326. This is indicated schematically by a spirit level 34. The alignment is carried out in such a way that the support points 325 and 326 are underlaid accordingly in order to set the exact verticality of the support 32. As soon as the carrier 32 is aligned exactly vertically, it stands at the same time also, due to the connecting traverse 30 parallel to the axis of the base unit 28, as indicated in FIG. 2 by a parallelism symbol in the connecting line of the attachment points A1, B1 or A2, B2 of the traverse elements 301 and 302.

The structural units to be coupled to the base unit 28 parallel to the axis, ie. H. in this embodiment, the storage table 24 with its stacking devices and the fixing station 23 are fixed. The storage table 24 shown in FIG. 1 actually contains an entire stacking device. It is readily conceivable that this stacking table 24 must perform a vertical lifting or lowering movement during operation, which is dependent on the stack height of the stored recording medium 11 which is being formed. The vertical guide for the stacking table 24 is arranged in the side parts 322 of the carrier 32. A running profile 327 is schematically indicated in FIG. 3, in which the work table 24 is guided over rollers 241. A crawler chain 35 is also shown schematically, which runs via a drive pinion 36. The crawler chain 35 is fixed on one side in a side part 322 of the carrier 32 and is connected at its other end to the stacking table 24. Depending on the direction of rotation of the drive pinion 36 driven by a motor, the stacking table 24 is then raised up or lowered down.

In order to achieve this function, again in an axis-parallel assignment to the base unit 28, the running profiles 327 are inserted into a receptacle of the side parts 322 of the carrier 32, which is shown schematically in FIG. 3, as indicated in point D of FIG. 3. In addition, as indicated in point H of FIG. 3, these side parts accommodate the drive unit described for the upper part of the work table. The work table 24 with its integrated rollers 241, which is suspended in the side parts 322 of the carrier 32, is thus assigned to the other structural units of the printer parallel to the axis.

The fixing station 23 is connected via two further connecting pins 37 in points C1 and C2, respectively, in the side parts 322 of the carrier 32. FIG. 2 illustrates that it is brought into contact at a point G with respect to one of the side parts 322 of the carrier 32. In particular, FIG. 3 illustrates that the fixing station 23 is supported as a support point at a point F fixed to the housing. This support point F and the contact point G form the two fixed points for the arrangement of the fixing station 23 rotatably arranged in the attachment points C1, C2. It is thus coupled in parallel to the other structural units of the printer in such a way that the fixing station 23 in the longitudinal expansion caused by heat specified directions v and w, ie the corresponding degrees of freedom remain in the axial direction and perpendicular to it. This coupling of the fixing station 23 is particularly important because, in addition to the possibility of length expansion, this also creates the prerequisite that the fixing station 23 can be replaced as an independent structural unit at any time without special adjustment processes simply by hanging it in the carrier 32.

The exemplary embodiment described above explains the principle of this construction concept and can be expanded beyond the selected example. So it would be conceivable, for example, also parts of the units of the electrophotographic printer assigned to the base unit, such as, for. B. mechanically couple the input tray in a similar manner with the other components of the printer. The invention is therefore not limited to the mechanical coupling of the structural units described.

Claims (11)

1. Electrophotographic printer or copier having a machine skeleton (1), a basic unit (28) which has a printing assembly (15) and is arranged with its major axis in a plane parallel to the transport path of a recording carrier (12), perpendicularly to the direction of transport of the latter, and further constructional units (23, 24) which are coupled mechanically to the basic unit and the major axes of which are oriented parallel to one another and to the major axis of the basic unit, characterised in that there are provided a bearer (32), arranged on the machine skeleton, and a crossmember (301, 302) which is respectively connected rotationally movably to the basic unit (at A1, A2) and to the bearer (at B1, B2), at two receiving points located in the direction of these major axes and remote from one another, in planes perpendicular to these major axes, in that adjustment means are provided for orienting the bearer vertically with the machine skeleton, and in that the further constructional units are respectively articulated on the bearer in paired receptacles (C1, C2), the connecting lines of which are themselves oriented parallel to the major axes.
2. Electrophotographic printer or copier according to Claim 1, characterised in that the crossmember (30) consists of two crossmember elements (301, 302) uncoupled from one another, and in that the bearer (32) of U-shaped basic form has two side parts (322) which stand vertically in the installed state and which are connected rigidly to one another via a base part (321) resting on the machine skeleton (1) and oriented parallel to the major axes, and in that the crossmember elements are articulated rotatably each independently on the basic unit (28) and on one of the side parts (322).
3. Electrophotographic printer or copier according to Claim 2, characterised in that the base part (321) of the bearer (32) has three resting points (325 and 326), at which it is vertically orientable with respect to the machine skeleton (1) in the state already articulated on the basic unit (28) via the crossmember (30 or 301, 302).
4. Electrophotographic printer or copier according to Claim 2 or 3, characterised in that the side parts (322) of the bearer (32) each have an arm (323) projecting laterally transversely to the major axes and having a bearing lug (324), on which one end of each of the crossmember elements (301 or 302) is respectively articulated rotatably via a connecting element (33), the other ends of the crossmember elements being respectively articulated on one of two bearing lugs (29) of the basic unit (28) via a further connecting element (31).
5. Electrophotographic printer or copier according to one of Claims 1 to 4, characterised in that a fixing station (23) of the printer or copier and/or a paper-stacking device (24) each form one of the constructional units to be coupled to the basic unit (28).
6. Electrophotographic printer or copier according to one of Claims 2 to 5, characterised in that the constructional unit to be coupled, especially the fixing station (23), is respectively suspended rotationally movably at one of two receiving points (C1 and C2) arranged mirror-symmetrically to one another in the side parts (322) of the bearer (32), and on the housing skeleton (1) or on the bearer (32) there is provided a resting point (F) at which this constructional unit is supported vertically.
7. Electrophotographic printer or copier according to Claim 6, characterised in that a bearing face (G) is provided on the bearer (32), for the constructional unit (23) to be coupled, as a reference line for the orientation of the constructional unit parallel to the major-axes direction.
8. Electrophotographic printer or copier according to one of Claims 2 to 5, characterised in that the side parts (322) of the bearer (32) each have a running profile (327), and in that a constructional unit to be coupled, especially a lowerable delivery table (24) for a stack of recording carriers (12), possesses laterally arranged running rollers (241) which are inserted into the running profiles, at least one of the running rollers being at a predetermined vertical distance from the others, and in that vertical supporting means (for example 35, 36) are provided for the constructional unit to be coupled.
9. Electrophotographic printer or copier according to Claim 8, characterised in that the constructional unit (24) to be coupled is arranged vertically displaceably in the side parts (322) of the bearer (32), the supporting means being designed as raising and lowering means (35, 36) which allow a vertical movement of the running rollers (241) in the running profiles (327).
10. Electrophotographic printer or copier according to Claim 9, characterised in that the raising and lowering means consist respectively of a motor-driven pinion (36), mounted rotationally movably in the side parts (322) of the bearer (30) above the displaceably arranged constructional unit (24), and of a chain (35) which is in engagement with the pinion and the ends of which are fastened fixedly in place or are articulated on the constructional unit (24).
11. Electrophotographic printer or copier according to Claim 10, characterised in that receptacles for the pinion (36) coupled to a drive unit, for the chain (35) and/or for running rails which form the running profiles (327) are provided in the side parts (322) of the bearer (32).

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