Device and method for printing on the edges of stationery products, particularly books

Abstract

The invention relates to a device for printing the edges of stationery products, particularly books. The device for printing the edges of stationery products, particularly books, comprises a body (8), a device controller, a printing module (1) with a print controller and a printhead (1A), as well as a gripping assembly (2) with a pair of rotating clamping jaws (2A, 2B) provided with clamping jaw lining (3) adapted to hold a workpiece (4) consisting of stationery products, particularly books, between them. The invention is characterised in that at least one jaw in the pair of rotating clamping jaws (2A, 2B) is mounted slidably and is coupled with a drive assembly (10) connected to this sliding clamping jaw (2A). The device includes a system for controlling the clamping force of the sliding clamping jaw (2A) and a measurement system for reading the position of the drive assembly (10) of the sliding clamping jaw. The measurement system for reading the position of the drive assembly (10) is connected to the device controller. The invention also relates to a method for printing the edges of stationery products, wherein the clamping force of the clamping jaws (2A, 2B) is input into the device controller, and a reference position of the clamping jaws (2A, 2B) is established for which a reference width of the workpiece (4) and the position of the drive motor of the clamping jaws (2A, 2B) are determined, and after forming the workpiece (4), its actual width is determined by comparing the position of the drive motor of the clamping jaws (2A, 2B) after forming the workpiece (4) with the position of the drive motor of the clamping jaws (2) in the reference position. Based on the measurement of the actual width of the workpiece, the printing process of the selected edge of the workpiece (4) is then controlled.

Description

[0001] Device and method for printing on the edges of stationery products, particularly books

[0002] The subject of the invention is a device and a method for printing on the edges of stationery products, particularly books. These solutions are primarily applicable in industrial printing and bookbinding processes carried out on an industrial scale. The device and method can be used for printing on the edges of all types of sheet-based stationery products. In particular, this includes the edges of books, as well as the edges of other stationery products such as calendars, notebooks and notepads, as well as the edges of marketing products like blocks of note pads or the edges of coasters for mugs, glasses and beer mugs, and the edges of other items that can be stacked for processing and have an imperfectly uniform thickness.

[0003] The vast majority of stationery products, regardless of whether they are printed, like books, or unprinted, like notepads and exercise books, consist of multiple sheets bound together. Typical stationery products take the form of a cuboid, in which the spine, top edge, front edge and bottom edge can be distinguished. To enhance the aesthetics of stationery edges, various methods of decorating the abovementioned edges are used. The prior art includes printing decorations, images and graphics on book edges, including printing on all three edges of books.

[0004] Document CN111572213A discloses a device for printing on the edges of books using pigment printing or UV printing. The device comprises a movable, four-position reel that rotates counterclockwise. The positions are arranged at 90° intervals, and each contains a pair of clamping jaws, consisting of a fixed jaw and a movable jaw. At the first position, at the bottom of the reel, a stack of books is loaded to form the workpiece. At the second position, to the right of the first, the edge of the stack intended for printing is cleaned. This cleaning removes dust and paper particles generated during the cutting of the workpiece. At the third position, at the top of the reel, one edge of the stack of books is printed. The printing assembly has a narrow printhead mounted on a carriage that moves multiple times over the stack of books while printing one side of the stack. The next, fourth position is used for unloading the stack of books. The movable reel allows for continuous loading and unloading of book stacks while other operations, such as cleaning and printing, are taking place. Each position of the device has a pair of clamping jaws that hold the stack of books. A positioning plate is used between the clamping jaws to align the stack. In each pair of jaws, one jaw is fixed, while the other is sliding and presses the book stack to a predetermined size, ensuring uniformity of the printing surface across different batches of books. Additionally, the device includes a mechanism for measuring the stroke of the sliding jaw, allowing for adjustments of the stroke of that jaw via its drive mechanism.

[0005] In practical applications, a book edge printing device is also known from Durrer Spezialmaschinen AG, marketed underthe name DIGI-B. In the device datasheets and marketing videos, a book-edge printing device was revealed, using a single-pass printhead. The device enables the printing of all three book edges in a single technological process. The system uses a robot that picks up the book stack from the loading area, rotates the book stack during the printing process and delivers the printed stack to the unloading area. The robot grips the book stack using a pair of rotating clamping jaws. The loading and unloading of book stacks are performed manually by an operator at the same station where the robot's clamping jaws pause. The operator places the stack directly between the clamping jaws of the robot. The clamping jaws move between two extreme positions: an open position, allowing the operator to load the book stack, and a closed position, in which the device transports the book stack under the printhead. The edges of the books are printed with their spine axis oriented perpendicularly to the line of nozzles located on the printhead, meaning the books are positioned perpendicular to the printing direction.

[0006] The clamping jaws used in prior art solutions allow for proper compression of the book stack, the workpiece, to a predefined and fixed width. The clamping jaws have two set positions - one in which the workpiece can be inserted between the clamping jaws and another in which the workpiece is clamped. Consequently, known devices perform printing using a single fixed clamping jaw position for a defined workpiece width, ensuring that the workpiece remains compressed. Prior art devices do not provide real-time control of clamping force. This creates the risk of inadequate clamping pressure, which can negatively impact the entire book edge printing process. One risk arising in such situations from insufficient clamping if the workpiece is the potential dropping and damage of books, which may lead to machine stoppage and unplanned production downtime. Another risk is related to variations in the width of the book stack caused by paper thickness tolerances. This can result in the print being positioned incorrectly on the book, affecting quality, for example, misaligned prints or, in some cases, rendering the product unusable, when an adjacent book's graphic is printed on the edge of the book, or when the outermost book remains unprinted.

[0007] The differences in the width of stacks of books arise from tolerances in paper grammage and thickness. According to manufacturers' declarations, the tolerance for grammage measured in accordance with ISO 536 is + / -2% or + / -3%. The tolerance for thickness in accordance with ISO 534 is also + / -3%. Both discrepancies may occur simultaneously and can reach + / -€>%, for example, in a situation where, in one batch of paper, the grammage is at its lower permissible tolerance and is -3% from the nominal grammage, while in another batch of paper, the grammage is at its upper permissible tolerance and is +3% from the nominal grammage. In addition to the tolerance for paper grammage, there is also the tolerance for its thickness. An example of paper available on the market with a grammage tolerance specified in g / m2as + / -3% is Amber Graphic paper, produced by Arctic Paper Kostrzyn S.A. The aforementioned paper is also characterised by a thickness tolerance specified in micrometres within a range of + / -2% to + / -3%. In particular, differences in grammage and thickness of paper may occur between different production batches, meaning that, for instance, books made from different batches of paper will differ in their actual thickness. Consequently, in practice, stationery products made from different batches of paper will have varying grammages and thicknesses of individual sheets, which will remain within tolerance limits.

[0008] In known solutions, in order to minimise production waste, appropriately designed graphics are selected to match the width of the stack of stationery products, especially to avoid excessive graphic overlap onto an adjacent product or leaving an unprinted surface area.

[0009] The objective of the invention is to solve the technical problem of insufficient print quality on the edges of stationery products and to reduce, or even completely eliminate, quality issues. The invention also aims to improve the efficiency of devices used for printing on the edges of books, which is constrained by the difficulty of adequately compressing the stack of stationery products during printing.

[0010] The first invention concerns a device for printing on the edges of stationery products, particularly books, comprising a body, a device controller, a printing module with a print controller and a printhead, and a gripping assembly with a pair of rotating clamping jaws provided with clamping jaw linings adapted to hold between them a workpiece of stationery products, particularly books. The essence of the invention lies in the fact that at least one jaw in the pair of rotating clamping jaws is slidably mounted and is coupled with a drive assembly connected to this sliding clamping jaw, wherein the device includes a control system for controlling the clamping force of the sliding clamping jaw and a measurement system for reading the position of the drive assembly of the sliding clamping jaw, wherein the measurement system for reading the position of the drive assembly of the sliding clamping jaw is connected to the device controller.

[0011] In this description:

[0012] - workpiece is understood to mean a stack of stationery products, particularly books, placed in the gripping assembly of the device for printing on book edges, - workpiece width is understood to mean the size of the workpiece corresponding to the distance between the clamping jaw linings of the rotating clamping jaws,

[0013] - length of the graphic file is understood to mean the dimension of the graphic file for printing on the edges of stationery products, corresponding to the workpiece width.

[0014] The advantage of such a solution is the elimination of technical issues resulting from the variable actual width of the workpiece - stationery products, particularly books intended for printing. The workpiece is compressed in the clamping jaws with an adequate force set during process preparation, which force not only can be established but also measured. For this force, the position of the sliding clamping jaw after compressing the workpiece is determined and read by measuring the position of the drive assembly of this sliding clamping jaw. In the case of rotary motors, reading the position of the drive assembly means reading the rotational angular position of such a motor. This position can be read, for example, by reading the position of a servo encoder. In contrast, in the case of drive assemblies using electric linear motors or magnetic or pneumatic actuators, reading the position of the drive assembly means measuring the position of their selected element, such as a piston. This allows, firstly, for the workpiece to be compressed with a determined force that is appropriately adjusted, eliminating the risk of improper compression, particularly compression of the workpiece that is too weak. It also eliminates the risk of compressing the workpiece with excessive force that could damage the stationery products. Thanks to the control of the clamping force and the position of the sliding clamping jaw, the device ensures a repeatable clamping force for each workpiece, regardless of its actual dimensions, which vary due to the tolerances of paper parameters. The ability to measure the geometric size in the form of the width of each workpiece based on the position of the sliding clamping jaw, at a constant clamping force, allows precise placement of the print on each stationery product, significantly improving quality and eliminating the issue of misaligned prints in the wrong place in a book or graphics spanning across adjacent stationery products. Determining the actual workpiece width enables the appropriate selection of the graphic file length to match the actual print area. By defining the actual workpiece width, production waste is significantly reduced, improving the overall efficiency of the printing process.

[0015] For example, in the case of a workpiece - a stack of books with a nominal width of 210 mm, the difference between the narrowest and widest stack may be 25 mm. Consequently, even for such variations, a predetermined constant clamping force can be applied regardless of the actual workpiece width. Moreover, reading the exact position of the sliding clamping jaw allows not only for determining the actual width of the workpiece intended for printing but also enables methods to adjust the nominal graphic file to the actual workpiece width. To this end, using a constant clamping force and measuring the width of the compressed workpiece, an appropriate printing method should be selected, ranging from adjusting the speed at which the workpiece moves under the printhead, through the method that includes selecting a file of suitable length for printing, to the method that involves rasterisation of the graphic file in real-time.

[0016] Preferably, the drive assembly of the sliding clamping jaw comprises a rotary motor, and the measurement system for reading the position of the drive assembly includes a transducer for determining the rotational angular position of the rotary motor shaft.

[0017] It is advantageous if the drive assembly of the sliding clamping jaw comprises a servomechanism. The use of such drive systems allows for a simple and reliable device construction to be made, which also does not create difficulties during operation and maintenance. Furthermore, the use of servomechanisms enables easy determination of linear motion data, particularly thanks to integrated sensors for determining the position, speed of the motor rotor and torque. The use of additional sensors is also straightforward. This results in low failure rates and ease of control. It is also preferable if the drive assembly of the sliding clamping jaw comprises a pneumatic actuator with a control valve, and the measurement system for reading the position of the drive assembly of the sliding clamping jaw includes a transducer for determining the linear position of the piston of the pneumatic actuator. This is also a simple and reliable device construction, which is based on a drive assembly for the sliding clamping jaw other than a motor.

[0018] Particularly advantageously, the device comprises a single-pass printhead having at least one line of nozzles. This significantly increases the efficiency of printing on the edges of books by avoiding multiple movements of a narrow printhead over the edge of the workpiece.

[0019] It is preferable that the longitudinal axis of the rotating clamping jaws, along which the sliding clamping jaw is moved, is perpendicular to the line of nozzles of the printhead. Alternatively, the longitudinal axis of the rotating clamping jaws, along which the sliding clamping jaw is moved, is parallel to the line of nozzles of the printhead. The use of different orientations of the clamping jaws relative to the printhead allows the device to be adapted to specific conditions and the needs of users of such devices. In any orientation, however, the system for controlling the clamping force of the sliding clamping jaw and the measurement system for reading the position of the drive assembly of the sliding clamping jaw are maintained, ensuring high-quality printed book edges and minimal waste.

[0020] The second invention concerns a method for printing on the edges of stationery products, wherein: a nominal graphic file for printing, having a defined length, is input into the print controller of the printing device, a stack of stationery products is placed in the clamping jaws of the printing device, which have clamping jaws linings, and it is aligned to form a workpiece; the selected edge of the stationery products forming the workpiece is then printed under the printhead based on the input nominal graphic file, wherein, after printing the selected edge: the workpiece is rotated around its longitudinal axis and another selected edge of the stationery products is printed under the printhead, or the printing process is completed,

[0021] The essence of this invention lies in the fact that the clamping force of the clamping jaws is input into the device controller, and a reference position of the clamping jaws is established, for which the reference width of the workpiece and the position of the drive assembly of the clamping jaws are determined. After forming the workpiece, its actual width is determined by comparing the position of the drive assembly of the clamping jaws after forming the workpiece with the position of the drive assembly of the clamping jaws in the reference position, and subsequently, the printing process of the selected edge of the workpiece is controlled accordingly.

[0022] By reading the rotational angular position of the drive motor of the clamping jaws, the actual width of the compressed workpiece can be easily determined. For this purpose, in particular, encoders and resolvers with large ranges of registered shaft rotation angles can be used. The use of encoders and resolvers in servomechanisms and stepper motors does not pose difficulties. This printing method enables the printing of the edges of stationery products with a significant reduction in defects. In solutions where the dimensions of the printed object are not controlled, the printed image is often too large, resulting in the graphic spanning between adjacent books, or the printed image is too small, which can lead to both the graphic spanning between adjacent books and the presence of an unprinted area. These are critical problems that cause high waste rates. By determining the actual size of the print area, it is possible to appropriately control the subsequent printing process, eliminating the primary cause of defective prints resulting from, among other factors, the tolerance of paper weight and thickness, as previously discussed. As with the device, measuring the actual size of the workpiece eliminates technical issues arising from its variable actual width.

[0023] It is particularly advantageous when the selected edge of the stationery products forming the workpiece is printed using a single-pass printhead, and the printing process of the selected edge of the workpiece is controlled using one of the following methods:

[0024] - a method in which the actual width of the workpiece is compared with the length of the input nominal graphic file, and the difference between the width of the workpiece and the length of the input nominal graphic file is calculated as a relative percentage value, and then based on this comparison, the guiding speed of the workpiece under the printhead or the guiding speed of the printhead over the workpiece is controlled, such that:

[0025] - if the actual width of the workpiece is smaller by a predetermined value than the length of the nominal graphic file, the guiding speed is reduced by the same predetermined value relative to the guiding speed input into the print controller, which is used by its printing control algorithm; and

[0026] - if the actual width of the workpiece is greater by a predetermined value than the length of the nominal graphic file, the guiding speed is increased by the same predetermined value relative to the guiding speed input into the print controller, which is used by its printing control algorithm;

[0027] - a method in which, prior to the printing process, in addition to the input nominal graphic file, graphic files of greater and lesser lengths than the nominal graphic file are also input, and then a graphic file of appropriate length is selected based on the determined actual width of the workpiece;

[0028] - a method in which the graphic file is rasterised in real-time to match the measured actual width of the workpiece. It is evident that the methods are selected according to the current requirements of the book edge printing process. The first method, which involves adjusting the guiding speed, allows for simple, rapid and automated adaptation of the graphic size to the actual print area. The change in the guiding speed of the gripping assembly underthe printhead has only a minimal, imperceptible to the naked human eye effect on print quality. Meanwhile, the automated selection of a pre-prepared graphic file of a length adjusted to the width of the workpiece is also a fast method that supports high efficiency and consistent quality. Before the printing process begins, a set of graphic files with lengths greater and smaller than the nominal graphic file length can be prepared. During printing, selecting the appropriate file does not affect the overall process time. A more time-consuming and therefore less efficient method is the realtime rasterisation of the image for each successive workpiece, particularly for large graphic files. While this method is time-consuming, it enables the generation of files adjusted to the actual width of the workpiece. Furthermore, rasterising the graphic file for each successive workpiece within the relatively short time required to print a single workpiece, which involves processing often very large graphic files, necessitates the use of device components with high computing power.

[0029] It is particularly advantageous if the guiding speed of the workpiece is varies within a range of -10% to +10%. This range is expected to be the most commonly used speed adjustment parameter, and modifying the printing speed within this range will not cause a noticeable deterioration in print quality.

[0030] The primary advantage of the inventions is therefore the high quality of printed edges of stationery products, particularly books. Additionally, device efficiency has been increased by eliminating unplanned production downtimes resulting from insufficient clamping force on the workpiece, which previously led to books being dropped and damaged, thereby also causing device stoppages. The above advantages result from ensuring a repeatable clamping force for each workpiece, regardless of its actual width, which varies due to paper parameter tolerances, while simultaneously determining this actual workpiece width.

[0031] The invention is presented in embodiments and in the drawing, which illustrates in:

[0032] Fig. 1 - a schematic layout of the clamping jaws and the direction of printing of the stack in a top view in the first embodiment;

[0033] Fig. 2 - a device for printing the edges of stationery products in the first embodiment in a side view;

[0034] Fig. 3 - the device as in Fig. 2 in a top view,

[0035] Fig. 4 - the device as in Fig. 2 in another side view;

[0036] Fig. 5 - a schematic layout of the clamping jaws and the direction of printing of the workpiece in a top view in the second embodiment.

[0037] The printing device comprises a printing module 1 (Fig. 1) with a single-pass printhead 1A and a gripping assembly 2 with a pair of rotary clamping jaws 2A, 2B. The printhead 1A enables printing using the direct-to-shape inkjet technology and allows the printing of an entire single edge of an object in a single pass. The printhead 1A has a width of 300 mm, corresponding to the capability of printing on A4 format products. The printhead 1A includes lines of nozzles that generate ink droplets, which then land on the material to be printed. A straight line L passes through the selected line of nozzles of the printhead 1A. The printing device can employ any type of printing technology, particularly printers using pigment, dyebased, UV and solvent inks. Such printheads 1A are known in the prior art.

[0038] In the pair of rotating clamping jaws 2A, 2B, one clamping jaw is driven and constitutes the movable clamping jaw 2A, while the other is a fixed clamping jaw 2B. The clamping jaws 2A, 2B are equipped with clamping jaws linings 3 adapted for placing between them a workpiece 4 of stationery products, especially books 5. Typically, rigid cardboard spacers 6 are placed between the products forming the workpiece 4. The clamping jaws linings 3 are replaceable and detachably connected to the clamping jaws 2A, 2B. This allows for their replacement and adjustment in shape to match the stationery products forming the workpiece 4.

[0039] The rotating pressure jaws 2A, 2B are constructed as one fixed clamping jaw 2B, i.e., a jaw with a fixed, predetermined linear position, and one movable clamping jaw 2A. The clamping jaws 2A, 2B are also synchronously rotated about their longitudinal axis O2 by a selected angle. The longitudinal axis O2 of the rotating clamping jaws 2A, 2B is also the axis along which the sliding clamping jaw 2A is displaced. The longitudinal axis O2 of the rotating clamping jaws 2A, 2B is perpendicular to the line of nozzles of the printhead, and thus, in the top view, is perpendicular to line L. To achieve rotation of the clamping jaws 2A, 2B, each of the clamping jaws 2A, 2B has its own motor 14 that executes the rotational movement of the jaw along with its lining 3. Consequently, the rotating clamping jaws 2A, 2B rotate the workpiece 4 about its axis of symmetry Oi, which is perpendicular to the line of nozzles of the printhead 1A. This corresponds to a rotation around the X-axis in a Cartesian coordinate system.

[0040] The sliding clamping jaw 2A is coupled with a drive assembly 10 that includes a servomechanism connected via a screw transmission to the sliding clamping jaw 2A. After placing the workpiece 4 between the clamping jaws 2A, 2B, it is pressed by the sliding clamping jaw 2A against the fixed clamping jaw 2B. The gripping assembly 2 is connected to a control system regulating the clamping force of the sliding clamping jaw 2A and comprises a measuring system that reads the angular rotational position of the drive of the sliding clamping jaw 2A, and thus indirectly determines the exact position of the sliding clamping jaw 2A and the distance from the fixed clamping jaw 2B. To this end, as mentioned, a servomechanism with a high-precision encoder has been used. The fixed clamping jaw 2B has an immobile linear position but, as indicated earlier, is also a rotating jaw. Another advantageous example of the drive assembly 10 for the sliding clamping jaw 2A is a stepper motor with an assigned encoder or a high-precision resolver.

[0041] Arranging the rotating clamping jaws 2A, 2B with their longitudinal axis perpendicular to the line of nozzles of the printhead 1 has a positive impact on print quality. The device performs edge printing of books using the bleed printing method, in which it is necessary to use graphics files larger than the actual dimensions of the product to ensure full coverage of the product's surface. By using clamping jaws 2A, 2B oriented with their longitudinal axis perpendicular to the line of nozzles of the printhead 1, and consequently aligning the sheet edges through which straight line K passes, designated for printing in a given printing cycle, parallel to the line of nozzles of the printhead 1, the ink cloud from the printer will settle in space 7 directly adjacent to the edges of the workpiece 4 and will not impact those edges.

[0042] The sliding clamping jaw 2A, together with the drive assembly 10, enables the gripping of a workpiece 4 of varying width and the clamping of the workpiece 4 with a constant force, regardless of its actual width. Proper clamping of the workpiece 4 is crucial, as insufficient clamping of the workpiece 4 may cause the displacement or loosening of the stationery items within the device, leading to production downtime. Conversely, excessive clamping of the workpiece 4 may damage or deform the workpiece 4. The applied measurement systems allow for the reading of the actual width of the workpiece 4 by comparing the position of the sliding clamping jaw 2A pressing the workpiece 4 against a reference position of the sliding clamping jaw 2A, for which the distance between the clamping jaws lining 3 surfaces corresponding to the workpiece width is known, as well as the rotational angular position of the servomechanism 10. Based on the change in the rotational angular position of the servomechanism 10, read for instance by an encoder, the actual width of the workpiece 4 after clamping can be determined.

[0043] The device, according to the first embodiment of the invention, comprises a body 8 with a horizontal rail 9, on which a printing module 1 is movably mounted, comprising a single-pass printhead 1A. In this embodiment, the printhead 1A utilises pigmentbased ink due to its high print durability, quality of printed graphics and colour stability. The printing module 1 is associated with a drive assembly 10 containing a servomechanism with a screw transmission. This ensures smooth movement and operation of the printing module along the entire length of the rail 9. Thus, the printing module 1 is movably mounted on the body 1 in the horizontal X direction.

[0044] The body 8 has a base 11 of the gripping assembly 2, which includes a pair of vertical guides 12, on which a slider 13 of the gripping assembly 2 is slidably mounted in the vertical Y direction. The slider 13 is equipped with the rotating clamping jaws 2A, 2B - the sliding clamping jaw 2A and the fixed clamping jaw 2B. The movement of the slider 13 along the vertical guides 12 is achieved via another drive assembly 10 containing a servomechanism with a screw transmission.

[0045] The gripping assembly 2 includes two rotating clamping jaws 2A, 2B with clamping jaws linings 3, having vertical, flat surfaces, which are beneficial for printing on cuboid-shaped stationery products such as books, notebooks and calendars. In this configuration of the clamping jaws 2A, 2B, the stack of stationery products forming the workpiece 4 is arranged with the edges of the sheets intended for printing aligned parallel to the line of nozzles of the printhead 1A. In this case, the longitudinal axis O2 of the rotating clamping jaws, along which the sliding clamping jaw 2A moves, is perpendicular to the line of nozzles of the printhead 1A.

[0046] The gripping assembly 2 and the printing module 1 are each assigned separate drive assemblies 10 to facilitate the movement of the printing module 1 in the horizontal X direction and the movement of the gripping assembly 2 in the vertical Y direction.

[0047] The applied measurement systems allow for the reading of the actual width of the workpiece 4 by comparing the position of the sliding clamping jaw 2A pressing the workpiece 4 against a reference position of the sliding clamping jaw 2A, for which the distance between the vertical lining 3 surfaces corresponding to the workpiece width is known, as well as the rotational angular position of the servomechanism 10. Based on the change in the rotational angular position of the servomechanism 10, read by an encoder, the actual width of the workpiece 4 after clamping can be determined.

[0048] The body 8, in the area of the base 11 of the gripping assembly 2, has a loading station 15 mounted on it. The loading station 15 has a retaining element 16, which is movably connected to the loading station 15 in the Z direction, parallel to the line of nozzles of the printhead 1A. The retaining element 16 is used to align and arrange the stationery items forming the workpiece 4 and subsequently to position the workpiece 4 in the Z direction, parallel to the line of nozzles of the printhead 1A, to a position where the horizontal symmetry axis Oi of the workpiece 4, which is perpendicular to the line of nozzles of the printhead 1A, aligns with the longitudinal axis O2 of the rotating clamping jaws 2A, 2B, along which the sliding clamping jaw 2A moves. The longitudinal axis O2 is also the axis of rotation for these rotating clamping jaws 2A, 2B. Therefore, the symmetry axis Oi of the workpiece 4 lies along the longitudinal axis O2 of the rotating clamping jaws, along which the sliding clamping jaw 2A moves.

[0049] Positioning the workpiece 4 in the Z direction, parallel to the line of nozzles of the printhead 1A, serves to adjust the position of workpieces 4 of different formats placed on the loading station 15 to the position of the rotation axis O2 of the clamping jaws 2A, 2B. Then, the horizontal symmetry axis Oi of the workpiece 4 is identical to the longitudinal axis O2 of the rotating clamping jaws 2A, 2B and to the rotation axis O2 of these clamping jaws 2A, 2B, which allows for better mechanical load distribution on the clamping jaws 2A, 2B and enables the use of a simpler algorithm for controlling the device's kinematics, as it maintains the symmetry of the workpiece 4 when rotated around its horizontal symmetry axis Oi. In alternative embodiments, the gripping assembly 2 can also be movably mounted in the Z direction, parallel to the line of nozzles of the printhead 1A, to achieve the same objective.

[0050] Additionally, the device is equipped with a controller for the device and a print controller, which are not shown in the drawings. These controllers provide control algorithms for the device, ensure smooth production processes and convert graphics into raster images. The device controller and print controller are connected to the system that controls the clamping force of the sliding clamping jaw 2A and the measurement system that reads the rotational angular position of the servomechanism assigned to the sliding clamping jaw 2A. This allows the actual width of the workpiece 4 to be measured after it has been placed between the rotating clamping jaws 2A, 2B and clamped. Based on these measurements, the printing process is subsequently controlled, either by proper management through the device controller or through the print controller. In particular, the device controller regulates the movement speed of the printing module 1 as it moves in the horizontal X direction. Meanwhile, the print controller can select the appropriate graphic file for printing or rasterise graphic files in real time, adjusting them to the measured actual width of the workpiece 4.

[0051] The workpiece 4 is oriented in the clamping jaws 2A, 2B so that the edges of the sheets intended for printing are parallel to the line of nozzles of the printhead 1A (Fig. 1). A straight line K passes through the edge of the sheets designated for printing, while a straight line L passes through the line of nozzles of the printhead. The lines K and L are parallel to each other. For the most common products, such as books, notebooks and calendars, the edges of the sheets intended for printing rarely exceed the size of an A4 sheet. The workpiece 4 may therefore have a width greater than the effective printing width of the printhead 1A, as adding additional stationery products to the workpiece 4 increases the width of the workpiece 4, while the height of the workpiece 4 corresponding to the height of the binding and the width of the printhead 1A remains constant. The width of the workpiece 4 is thus dependent on the quantity of printed materials and their thickness, and it is not limited by the width of the printhead. Consequently, a significant number of product copies can be printed in a single printing process. During operation, the gripping assembly 2 is positioned in the vertical Y direction to receive the workpiece 4 from the loading station 15, ensuring that, during collection of the workpiece 4, the symmetry axis Oi of the workpiece 4 lies along the rotation axis O2 of the linings 3 of the clamping jaws 2A, 2B. At the loading station 15, the sliding clamping jaw 2A closes with a force pre-set in the control system - the servomechanism achieves the designated torque. Simultaneously, the encoder transmits information to the device controller regarding the rotational angular position of the motor, based on which the control system calculates the width of the processed object after clamping, which is determined by comparing the current rotational angular position of the motor with the reference rotational angular position of the motor, for which the workpiece width is known. The difference between these values is calculated as a relative percentage. The method by which the printing process is conducted is then selected.

[0052] Subsequently, the gripping assembly 2, with the workpiece 4 clamped between the clamping jaws 2A, 2B, is positioned in the vertical Y direction to adjust the workpiece height relative to the printhead 1A. During this movement, the device controller performs the necessary measurements and calculations to determine the linear velocity of the movement of the printing module 1 as it moves horizontally in the X direction over the workpiece 2, or the print controller selects the appropriate graphic file. Next, horizontal movement is executed, during which the printing module 1 moves over the workpiece 4 and prints on the selected edge of the workpiece 4. After printing on one edge of the workpiece 4, the gripping assembly 2 rotates the workpiece 4 around its symmetry axis Oi, which is perpendicular to the line of nozzles of the printhead 1A. In the case of a workpiece 4 composed of cuboid-shaped stationery products such as books 5, this involves a 90° rotation. Following this, the printing module 1 moves back in the horizontal X direction, during which the next edge of the stationery products forming the workpiece 4, held by the gripping assembly 2, is printed. The described steps are repeated until all selected edges of the workpiece 4 are printed. Once all selected edges have been printed, the gripping assembly 2 moves back in the vertical Y direction to the loading station 15, where the clamping jaws 2A, 2B are released, and the printed product is left for collection by the operator. Once the printed workpiece 4 has been removed from the device, a new workpiece can be loaded, and the printing process can begin again.

[0053] The device's ability to rotate the workpiece 4 during a single process, ensuring continuous printing, i.e., printing all three edges of stationery products, particularly books, within one technological process, or even printing all three edges and the spine enhances the efficiency of the device and increases the production speed of printed batches, such as books, notebooks, calendars and similar products.

[0054] The device employs a printing method that begins with loading the nominal graphic file for printing into the print controller of the printing device, which has a defined length, and inputting into the device controller the clamping force values of the clamping jaws 2A, 2B for the workpiece 4. A reference position for the clamping jaws 2A, 2B is also established, at which the reference width of the workpiece 4 and the rotational angular position of the clamping jaw drive motor are determined. Next, a stack of stationery products is placed within the clamping jaws 2A, 2B and aligned to form the workpiece. After forming the workpiece 4, its actual width is determined by comparing the rotational angular position of the drive motor of the clamping jaws 2A, 2B after forming the workpiece 4 with the rotational angular position of the drive motor of the clamping jaws 2A, 2B in the reference position. This is achieved using readings from the encoders integrated into the drive assemblies 10, servomechanisms and the gripping assembly 2. Depending on the actual width of the workpiece 4 and current requirements, the printing process of the selected edge is controlled using one of three methods.

[0055] In the first method, after forming the workpiece 4, its actual width is determined. The actual width of the workpiece 4 is then compared with the size of the graphic in the input graphic file, and the difference between the width of the workpiece 4 and the size of the graphic is calculated as a relative percentage. Based on this comparison, the guiding speed of the printhead 1A over the workpiece 4 is adjusted according to the following principles: when the actual width of the workpiece 4 is smaller by a predetermined value of n% than the size of the graphic file, the guiding speed of the printhead 1A over the workpiece 4 is reduced by the same predetermined value of n% in relation to the speed input into the print controller, which is used by its print control algorithm, and when the actual width of the workpiece 4 is greater by a predetermined value of n% than the size of the graphic file, the guiding speed of the printhead 1A over the workpiece 4 is increased by the same predetermined value of n% in relation to the speed input into the print controller, which is used by its print control algorithm.

[0056] Thus, the guiding speed of the printhead 1A over the workpiece 4 is adjusted, while the operation of the printhead 1A, controlled by the print control algorithm implemented in the print controller, continues in the same manner as for the nominal speed - i.e., the speed of guiding the printhead 1A over a workpiece 4 of nominal width, as input into the print controller.

[0057] Obviously, in other embodiments, if the device's kinematics allow it, the guiding speed of the workpiece 4 under the printhead 1A can be controlled in the same manner, wherein the speed is adjusted relative to the guiding speed input into the print controller, which is used by the print control algorithm implemented in that print controller.

[0058] Examples of selecting the speed of guiding the printhead 1A over the workpiece 4 are presented in the table below. Measurements of the actual print area were conducted by determining the actual width of the workpiece. The variable width of the workpiece 4 during the production process results from differences in the grammage and volume of the paper. According to the paper manufacturer's declaration, the grammage tolerance is + / - 3% in accordance with ISO 536. The thickness tolerance is also + / - 3% in accordance with ISO 534. Both discrepancies may occur simultaneously, reaching up to + / - 6%. These tolerances apply to the vast majority of paper used in industrial production. For a workpiece with a maximum width of 210 mm, the difference between the narrowest and widest stack can be 25 mm, and the printing speed can vary between the minimum and maximum values by 12%. According to tests conducted on production trials with variable workpiece width, a change in workpiece width and the corresponding speed adjustment of + / -10% does not cause significant or visible distortions in the printed graphics that would be noticeable to the human eye.

[0059] Next, the printhead 1A is guided over the workpiece 4 at a predetermined speed, and the selected edge of the books forming the workpiece 4 is printed based on the input graphic file and the production file, which contains information on the stack geometry and the number of edges to be printed. After printing the selected edge of the workpiece 4, it is rotated around its axis of symmetry Oi, which is perpendicular to the line of nozzles of the printhead 1A, and it is then guided once more under the printhead 1A, and the next selected edge of the workpiece is printed. The process of rotating and printing continues until all edges of the workpiece have been printed in accordance with the production file. Once all edges of the workpiece 4 have been printed, the workpiece is guided to the receiving station 15, where the clamping jaws 2A, 2B of the gripping assembly 2 are released, marking the end of the process.

[0060] The method for printing the edges of stationery products, particularly books, allows for the verification of the workpiece 7 width at the start of each operation and the application of one of three methods for adjusting the length of the printed image to the actual width of the workpiece 7.

[0061] In another method of controlling the printing process, after determining the actual width of the workpiece 4, the nominal graphic file for printing is rasterised to match this determined actual width of the workpiece 4. To achieve this and ensure high efficiency, the print controller is equipped with components that provide high computational power.

[0062] In the next method of controlling the printing process, graphic files with lengths both greater and smaller than the length of the nominal graphic file are introduced into the print controller. The additional graphic files introduced have lengths up to 6% shorter and longer than the nominal file. The lengths of the prepared individual files vary in increments of 0.5%. In this embodiment, after determining the actual width of the workpiece 4, the measurement system transmits this information to the print controller, where an appropriate graphic file is selected to best match the determined actual width of the workpiece 4.

[0063] In the second embodiment, the printing device has a modified kinematics of the gripping assembly's movement. Identically to the first embodiment, the individual components of the device are powered, and the gripping assembly contains a pair of rotating clamping jaws 2A, 2B (Fig. 5) equipped with clamping jaws linings 3 adapted to hold the workpiece 4 of stationery products - books 5 - between them. Within the workpiece 4, cardboard spacers 6 are placed between the books 5. In the gripping assembly, the longitudinal axis O2 of the rotating clamping jaws, along which the sliding clamping jaw 2A moves, is parallel to the line of nozzles of the printhead 1A. As in the previous embodiment, the sliding clamping jaw 2A is coupled with the drive assembly 10, which is connected to this sliding clamping jaw 2A. The device includes a system for controlling the clamping force of the sliding clamping jaw 2A and a measurement system for reading the position of the drive assembly 10 of the sliding clamping jaw. The measurement system reading the position of the drive assembly 10 is connected to the device controller. In this device, the workpiece 4 was also compressed by the sliding clamping jaw 2A with a predetermined clamping force, and the actual width of the workpiece 4 was measured. Based on this, as in the previous embodiment, the process of printing the edges of the workpiece 4 was controlled.

[0064] In the third embodiment, the device has a structure analogous to the first embodiment, with the difference that the drive assembly of the sliding clamping jaw uses a pneumatic actuator with a control valve. Thus, the clamping force of the sliding clamping jaw was controlled via the control valve of the pneumatic actuator. In turn, the measurement system reading the position of the drive assembly of the sliding clamping jaw was equipped with a transducer for determining the linear position of the pneumatic actuator's piston.

[0065] Legend

[0066] 1 - printing module

[0067] 1A - printhead

[0068] 2 - gripping assembly

[0069] 2A, 2B - rotating clamping jaws:

[0070] 2A - sliding clamping jaw

[0071] 2B - fixed clamping jaw

[0072] 3 - clamping jaw lining

[0073] 4 - workpiece

[0074] 5 - books

[0075] 6 - spacers

[0076] 7 - space where the cloud of falling ink will be located

[0077] 8 - body

[0078] 9 - horizontal body rail

[0079] 10 - drive assembly

[0080] 11 - gripping assembly base

[0081] 12 - vertical guides on the gripping assembly base

[0082] 13 - gripping assembly slider

[0083] 14 - rotational motors of clamping jaws 2A, 2B

[0084] 15 - loading station

[0085] 16 - retaining element

Claims

Claims1. A device for printing the edges of stationery products, particularly books, comprising a body (8), a device controller, a printing module (1) with a print controller and a printhead (1A), and a gripping assembly (2) with a pair of rotating clamping jaws (2A, 2B) provided with clamping jaw lining (3) adapted to hold between them a workpiece (4) of stationery products, particularly books, characterised in that at least one jaw in the pair of rotating clamping jaws (2A, 2B) is slidably mounted and is coupled with a drive assembly (10) connected to this sliding clamping jaw (2A), wherein the device includes a system for controlling the clamping force of the sliding clamping jaw (2A) and a measurement system for reading the position of the drive assembly (10) of the sliding clamping jaw, wherein the measurement system for reading the position of the drive assembly (10) of the sliding clamping jaw (2A) is connected to the device controller.

2. The device according to claim 1, characterised in that the drive assembly (10) of the sliding clamping jaw (2A) comprises a rotary motor, and the measurement system for reading the position of the drive assembly (10) includes a transducer for determining the angular rotational position of the rotary motor shaft.

3. The device according to claim 1 or 2, characterised in that the drive assembly of the sliding clamping jaw (2A) comprises a servomechanism.

4. The device according to claim 1, characterised in that the drive assembly (10) of the sliding clamping jaw (2A) comprises a pneumatic actuator with a control valve, and the measurement system for reading the position of the drive assembly (10) of the sliding clamping jaw includes a transducer for determining the linear position of the piston of the pneumatic actuator.

5. The device according to any of claims 1 to 4, characterised in that it comprises a single-pass printhead (1A) having at least one line of nozzles.

6. The device according to claim 5, characterised in that the longitudinal axis (O2) of the rotating clamping jaws, along which the sliding clamping jaw (2A) is moved, is perpendicular to the line of nozzles of the printhead (1A).

7. The device according to claim 5, characterised in that the longitudinal axis (O2) of the rotating clamping jaws, along which the sliding clamping jaw (2A) is moved, is parallel to the line of nozzles of the printhead (1A).

8. A method for printing the edges of stationery products, wherein: a nominal graphic file for printing, having a defined length, is input into the print controller of the printing device, a stack of stationery products is placed within the clamping jaws (2A, 2B) of the printing device, which have clamping jaws lining (3), and it is aligned to form a workpiece (4), the selected edge of the stationery products forming the workpiece (4) is then printed under the printhead (1A) based on the input nominal graphic file, wherein after printing the selected edge: the workpiece (4) is rotated around its longitudinal axis (O2) and another selected edge of the stationery products is printed under the printhead (1A), or the printing process is completed, characterised in that the clamping force of the clamping jaws (2A, 2B) is input, and a reference position of the clamping jaws (2A, 2B) is established, for which a reference width of the workpiece (4) and the position of the drive assembly of the clamping jaws (2A, 2B) are determined, after forming the workpiece (4), its actual width is determined by comparing the position of the drive assembly of the clamping jaws (2A, 2B) after forming the workpiece (4) with the position of the drive assembly of the clamping jaws (2) in the reference position,the printing process of the selected edge of the workpiece (4) is then controlled accordingly.

9. The printing method according to claim 8, characterised in that the selected edge of the stationery products forming the workpiece (4) is printed under a single-pass printhead (1A), and the printing process of the selected edge of the workpiece (4) is controlled using one of the following methods:A. a method in which the actual width of the workpiece (4) is compared with the length of the input nominal graphic file, and the difference between the width of the workpiece (4) and the length of the input nominal graphic file is calculated as a relative percentage value, and then, based on this comparison, the guiding speed of the workpiece (4) under the printhead (1A) or the guiding speed of the printhead (1A) over the workpiece is controlled, such that:- if the actual width of the workpiece (4) is smaller by a predetermined value (n%) than the length of the nominal graphic file, the guiding speed is reduced by the same predetermined value (n%) relative to the guiding speed input into the print controller, which is used by its printing control algorithm; and- if the actual width of the workpiece (4) is greater by a predetermined value (n%) than the length of the nominal graphic file, the guiding speed is increased by the same predetermined value (n%) relative to the guiding speed input into the print controller, which is used by its printing control algorithm;B. a method in which, prior to the printing process, in addition to the input nominal graphic file, graphic files of greater and lesser lengths than the nominal graphic file are also input, and then a graphic file ofappropriate length is selected based on the determined actual width of the workpiece (4);C. a method in which the graphic file is rasterised in real-time to match the measured actual width of the workpiece (4).

10. The printing method according to claim 9, characterised in that the guiding speed varies within a range of -10% to +10%.

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