CN109927415B

CN109927415B - Print head calibration apparatus and print beam

Info

Publication number: CN109927415B
Application number: CN201811547811.8A
Authority: CN
Inventors: A·米勒
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 2017-12-19
Filing date: 2018-12-18
Publication date: 2022-03-15
Anticipated expiration: 2038-12-18
Also published as: CN109927415A; DE102018219826A1

Abstract

The invention relates to a device for calibrating an inkjet print head (2), comprising a stop (3) and a shaft (14) for adjusting the stop (3), wherein the print head (2) rests directly or indirectly on the stop (3). The stop (3) and the shaft (14) are connected to each other by a compensating coupling device (5), the compensating coupling device (5) compensating for an axial path difference between the stop (3) and the shaft (14).

Description

Print head calibration apparatus and print beam

Technical Field

The invention relates to a device for calibrating an inkjet print head, comprising a stop and a shaft for adjusting the stop, wherein the print head rests directly or indirectly on the stop.

Background

Print heads to be aligned with one another are arranged in an array on a print beam for page-wide inkjet printing. For this purpose, stops are provided, for example in the form of cones, against which the printing heads rest, for example indirectly via a holder. Furthermore, a shaft is assigned to each stop, by means of which the stop can be moved, so that it presses the print head in the desired direction, or so that free space is freed, so that a spring can press the print head in the desired direction.

Such a printed beam is described in US 2009/0244124 a 1. In this printing beam, the shaft is screwed into the cone. A disadvantage is that such a construction is not sufficiently free of play and disturbing forces affecting the accuracy of the calibration may be transmitted from the shaft to the cone.

Disclosure of Invention

The object of the present invention is to provide a print head calibration device which operates more precisely.

This object is achieved by an apparatus for calibrating an inkjet print head, comprising a stop and a shaft for adjusting the stop, wherein the print head rests directly or indirectly on the stop, and the apparatus is characterized in that the stop and the shaft are connected to each other by a compensating coupling device which compensates for an axial path difference between the stop and the shaft.

The advantage here is that, by having sufficient play, a minimization of the movement delay is achieved. In the best case, no further forces, other than torque, are transmitted from the shaft to the stop by the compensating coupling. Another advantage is that the shaft can be driven by a direct drive fastened to the frame. The linear degree of freedom in the compensating linkage compensates for the path differences that arise during the adjustment of the stop relative to the frame and thus relative to the direct drive.

There are different possible modifications: the shaft may be a drive shaft and the stop may be arranged on an adjusting shaft (stellwell). The adjusting shaft can have an external thread, which together with the internal thread of the component can form a screw drive for the translational adjustment of the stop. The stop may be a cone. The compensating coupling device may have a first coupling half, a second coupling half, and an intermediate piece. The intermediate piece can be connected to the coupling halves by means of a snap connection (Schnappverbindung). The intermediate member may be a sleeve. The compensating coupling can have a sprung arm (Federarm). The compensating coupling can have guide grooves and drivers which engage in these guide grooves. The compensating coupling may be manufactured at least partly as a 3D printed product in an additive manner (additiv). The shaft may be an integral part of the motor or connected to the motor, wherein the motor may be fastened to the machine frame.

The invention also includes a printing bar comprising an inkjet print head array, to which at least one calibration device is assigned, which is designed according to the calibration device according to the invention or one of its variants.

Drawings

Advantageous refinements also result from the following description of an embodiment and from the drawings, in which:

FIG. 1: a side view of a printing press having a print beam;

FIG. 2: a top view of a print beam with a print head arrangement and calibration apparatus;

FIG. 3: a detailed view of a print head with a calibration apparatus;

FIG. 4: a print head and calibration apparatus set in a modified manner with respect to fig. 3;

FIG. 5: an individual view of the coupling middleware of the calibration apparatus; and

FIG. 6: a side view of the coupling intermediate.

Detailed Description

Fig. 1 shows a digital printing press in which a sheet is transported from a feeder to an outfeed via a plurality of stations by means of cylinders. One station comprises a plurality of printing beams 1 of identical construction for page-wide multicolour printing with inkjet. Each printing beam 1 prints a different color.

Fig. 2 exemplarily shows a printing beam 1 based on the viewing angle II. The printing beam 1 carries an array of print heads 2, which array of print heads 2 extends over the width of the sheet. The print heads 2 are provided with nozzles (not shown) from which ink is ejected perpendicular to the plane of the drawing of fig. 2. Each print head 2 is assigned a calibration device with a stop 3 and a spring 4. These calibration devices are used to adjust the print heads 2 relative to each other, which in the present example is done linearly along the print beam 1. However, other adjustment directions (for example in the sheet transport direction) or other adjustment movement forms (for example pivoting movements) are also possible.

Fig. 3 shows one of the print heads 2 and one of the calibration devices. The stop 3 is coupled by means of a compensating coupling 5 to an electric motor 6 fastened to a frame 7. The motor 6 is preferably a stepper motor. The print head 2 is carried by a holder 8 resting on the stop 3. However, it is also possible for the printing head 2 to rest directly on the stop 3 itself. The stop 3 is designed as a cone and forms a section of the adjusting shaft 9. The adjustment shaft 9 may also be referred to as cone shaft. In addition to the stop 3, the adjusting shaft 9 has further sections, namely: an adapter part 10 as a sliding bearing, and an external thread 11. The stop 3 is located between these adaptations 10. These adaptations 10 are slidably housed in one or more members 12. The component 12 has an internal thread 13, into which internal thread 13 the external thread 11 is screwed, wherein the adjusting shaft 9 and the component 12 together form a screw drive for the translational adjustment of the stop 3 in the x direction. The x-direction corresponds to the axis of rotation of the adjusting shaft 9. The print head 2 (or its holder 8) together with the stop 3 form a wedge drive which converts the movement of the stop 3 in the x direction into a movement of the print head 2 in the y direction, which is perpendicular to the x direction. Corresponding to fig. 3, the stop 3 is adjusted downwards so that the stop 3 presses the print head 2 to the left against the action of the spring 4. The stop 3 is adjusted upwards so that the stop 3 frees up free space for adjusting the print head 2 to the right by means of the spring 4.

The motor 6 rotates the adjusting shaft 9 via the compensating coupling 5, and in this case, depending on the adjusting direction, the adjusting shaft 9 is screwed slightly deeper into the component 12 or is screwed slightly out of the component 12. The adjusting shaft 9 is connected via the compensating coupling 5 to a drive shaft 14, which drive shaft 14 is the motor shaft of the motor 6 if the adjusting shaft 9 is adjusted in a motorized manner as in the present example. However, it is also possible to adjust the adjusting shaft 9 manually, for which purpose a handle (for example a knob) is fastened to the drive shaft 14 instead of the motor 6. The compensating coupling 5 comprises a first coupling half 15, a second coupling half 16 and an intermediate piece 17, the two

coupling halves

15,16 being connected to each other rotatably by the intermediate piece 17. The intermediate piece 17 is assembled with each

coupling half

15,16 by means of a snap connection. Thereby, an operator (e.g. during maintenance work) can disengage the snap connection structure in a tool-free manner to separate the motor 6 and the adjustment shaft 9 from each other. The compensating coupling 5 has a sprung arm for uncoupling and subsequent uncoupling, which is described in more detail below. The resilient arms may be located on the coupling halves 15,16, however, in a preferred construction, the resilient arms are arranged on an intermediate piece 17. This non-rotatable connection is achieved by means of teeth or catches which engage in the guide grooves 18. These drivers are also described in detail below. The guide slots 18 may be located on the sprung arms, however, in a preferred construction, the followers are disposed on the sprung arms. In the preferred configuration shown in the figures, the guide grooves 18 are introduced into the coupling halves 15,16, which are configured as hollow rollers or bushings. The guide grooves 18 run parallel to the axis of rotation of the coupling halves 15,16 and are arranged uniformly distributed along the inner circumferential surfaces of the coupling halves 15,16, for example one guide groove 18 per 90 °. The number of guide grooves 18 per

coupling half

15,16 and the number of spring arms corresponding thereto are preferably even, in this example four each. This is advantageous in terms of the diametrically opposed arrangement (diameterlen anchoring) of the spring arms and the guide grooves 18, which in turn is advantageous in terms of the formation of a universal joint (Kreuzgelenken). In order to realize these snap-in connections, locking limits (Rastschwellen) can be provided at the open ends of the guide grooves 18, which force the spring arms to compress briefly during the insertion. In the region of the locking limits, the depth of the guide grooves 18 is smaller, which is not shown in the figures for reasons of dimensional standards.

Fig. 4 shows the situation during adjustment, in which the adjustment shaft 9 is screwed deeper into the component 12 than in fig. 3. The motor 6 rotates the adjustment shaft 9 in order to move the stop 3 (cone) downwards and press the print head 2 to the left by means of the stop 3. The second coupling half 16 is fastened or formed on the adjusting shaft 9 and performs a translational movement with the adjusting shaft 9. The first coupling half 15 is fastened or formed on the drive shaft 14 and does not move with this second coupling half 16 in translation downwards, since the drive shaft 14 is fixedly connected with the motor 6, which motor 6 is in turn fixedly connected with the machine frame 7. Thereby, the second coupling half 16 is separated from the first coupling half 15, and a path difference occurs between the two

coupling halves

15, 16. This path difference is compensated for by the compensating coupling device 5 by axially displacing the intermediate piece 17 in one or both coupling

halves

15,16 along the guide grooves 18. Furthermore, the compensating coupling device 5 compensates for axial differences (axis fluchungsfehler) and angular differences Δ α that may be caused by tolerances when the motor 6 or the drive shaft 14 is mounted. In fig. 4, it can be seen that there is an angular difference Δ α between the drive shaft 14 and the adjusting shaft 9, and thus between the rotational axis of the first coupling half 15 and the rotational axis of the second coupling half 16, since the first coupling half 15 is connected coaxially with the drive shaft 14, while the second coupling half 16 is connected coaxially with the adjusting shaft 9. The intermediate piece 17, while compensating for the angular difference Δ α, executes a pivoting movement relative to the coupling halves 15,16 about a virtual pivot axis 19 oriented perpendicularly to the intermediate piece 17 and to the rotational axis of the coupling halves 15, 16. The pivot axis 19 is a component of a universal joint 20, which universal joint 20 is defined by the outer contour of the intermediate piece 17 inserted into the head of the coupling halves 15, 16.

Fig. 5 shows that the intermediate piece 17 has at each end a springing arm 21 as already mentioned above. These spring arms 21 are arranged in a star shape uniformly distributed along the circumference of the intermediate piece 17. Here, the ejection arm 21 on one end of the intermediate piece 17 is offset by a half-minute angle (Teilungswinkel) with respect to the ejection arm 21 on the other end, that is, by 45 ° in the case of a 90 ° minute angle in the present example, as shown in fig. 6. The resilient arms 21 of one end or head of the intermediate piece 17 are aligned with the gaps 22 between these resilient arms 21 on the other end of the intermediate piece 17. These sprung arms 21 extend longitudinally parallel to the axis of rotation 23 (see fig. 6) of the intermediate piece 17 and constitute a ring or loop in the form of tines or peaks on each end of the intermediate piece 17. These elastic arms 21 are more flexible in bending in the radial direction than in the circumferential direction of the intermediate member 17. By means of this radial flexibility, the elastic arms 21 compress inwards when the compensating coupling 5 is assembled. Another advantage derived from this radial flexibility is that: thereby achieving radial gapless. The rigid design of the sprung arms 21 in the circumferential direction is advantageous with regard to the transmission of torque.

On the outer side of these spring arms 21, the above-mentioned teeth or catches 24 are arranged, which teeth or catches 24 engage in the guide grooves 18 in the assembled state of the compensation coupling 5 in order to transmit a torque from the first coupling half 15 to the intermediate part 17 and from the intermediate part 17 to the second coupling half 16. The drivers 24 each have a circular-arc outer contour with a diameter D, wherein the circular-arc outer contours of two radially opposite drivers 24 lie on the same imaginary circle line whose center point is formed by the pivot axis 19. The circular-arc-shaped outer contour of the drivers 24 forms a pivot joint. In the example shown, for each end of the intermediate part 17, there are two pairs of diametrically opposed drivers 24 and thus two perpendicularly intersecting pivot axes 19 which together form the universal joint 20. In contrast, for each end, there may be, for example, six spring arms 21 and thus three pairs of diametrically opposed drivers 24, the universal joint 20 being formed by three pivot axes 19 offset by 60 ° from one another.

Fig. 6 shows that the intermediate piece 17 is a sleeve with a central through hole. In contrast, in the region of the intermediate webs 25 extending between the recesses 22 on the one end and the recesses 22 on the other end, the sleeve can have an intermediate wall which divides the hollow space inside the sleeve into two chambers which are each surrounded by a set or a ring of spring arms 21. In this case, instead of a central through-hole, the sleeve has two aligned blind holes. As also shown in fig. 6, the width of the drivers 24 decreases from the foot to the head of the drivers 24. Such a wedge-shaped cross section of the drivers 24 facilitates the compensation of play-free of the coupling device 5 in the circumferential direction. The obliquely descending flanks of the drivers 24 center them in the guide grooves 18. The shape of these drivers 24 is also advantageous in terms of the additive manufacturing of the intermediate piece 17 as a 3D printed product. These coupling halves 15,16 can also be made in an additive manner as a 3D printed product. In contrast to the illustrated embodiment, it is possible to design the drivers 24 as small cones, i.e. as conical teeth on the outer side of the spring arms 21, the center axes of which are oriented radially with respect to the intermediate piece 17.

List of reference numerals

1 printing beam

2 print head

3 stop part

4 spring

5 compensating coupling device

6 Motor

7 machine frame

8 holding member

9 adjusting shaft

10 fitting part

11 external screw thread

12 component

13 internal screw thread

14 drive shaft

15 coupling halves

16 coupling halves

17 intermediate member

18 guide groove

19 pivot axis

20 universal joint

21 springing arm

22 open space

23 axis of rotation

24 driving part

25 intermediate connecting bar

In the x direction

y direction

Delta alpha angle difference

Claims

1. An apparatus for calibrating an inkjet print head (2), the apparatus comprising a stop (3) and comprising a shaft (14) for adjusting the stop (3), wherein the print head (2) rests directly or indirectly on the stop (3),

it is characterized in that the preparation method is characterized in that,

the stop (3) and the shaft (14) are connected to one another by a compensating coupling device (5) which compensates for the difference in axial path between the stop (3) and the shaft (14), wherein the compensating coupling device (5) has a spring arm (21) which is compressed when the compensating coupling device (5) is assembled, thereby achieving a radial play-free of the compensating coupling device (5).

2. The apparatus as set forth in claim 1, wherein,

it is characterized in that the preparation method is characterized in that,

the shaft (14) is a drive shaft, and the stop (3) is arranged on an adjusting shaft (9), the adjusting shaft (9) being connected to the drive shaft by means of the compensating coupling (5).

3. The apparatus as set forth in claim 2, wherein,

it is characterized in that the preparation method is characterized in that,

the adjusting shaft (9) has an external thread (11) which, together with an internal thread (13) of a component (12), forms a screw drive for the translational adjustment of the stop (3).

4. The apparatus of any one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the stop (3) is a cone.

5. The apparatus of any one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the compensating coupling device (5) has a first coupling half (15), a second coupling half (16) and an intermediate piece (17).

6. The apparatus as set forth in claim 5, wherein,

it is characterized in that the preparation method is characterized in that,

the intermediate piece (17) is connected to the first coupling half (15) and to the second coupling half (16) by means of a snap connection.

7. The apparatus as set forth in claim 5, wherein,

it is characterized in that the preparation method is characterized in that,

the intermediate piece (17) is a sleeve.

8. The apparatus of any one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the compensation coupling (5) has a guide groove (18) and a driver (24) which engages into the guide groove (18).

9. The apparatus of any one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the compensating coupling device (5) is at least partially manufactured in an additive manner as a 3D printed product.

10. The apparatus of claim 2 or 3,

it is characterized in that the preparation method is characterized in that,

the drive shaft is a component of or connected to a motor (6), wherein the motor (6) is fastened to a frame (7).

11. Printing beam comprising an array of inkjet printing heads (2) each assigned at least one calibration device, which is constructed according to a device according to one of claims 1 to 10.