Pressure unit for a drive roller of a printing device

Abstract

Pressure unit (210) for a drive unit (150) for driving a web-shaped recording medium (120); wherein the pressure unit (210) comprises, - a pivoting arm (213) with a pressure roller (212), wherein the pivoting arm (213) is designed to pivot a main axis of rotation (211) away from or towards a drive roller (200) of the drive unit (150), so that a gap between the pressure roller (212) and the drive roller (200) is increased or decreased; - a fork (214) arranged on the swivel arm (213); - a camshaft (225) with a cam (222), wherein the camshaft (225) is designed to be rotated about a shaft axis of rotation (221), while the cam (222) is arranged in an opening of the fork (214), so that when the camshaft (225) is rotated, the pivot arm (213) is pivoted away from or towards the drive roller (200) of the drive unit (150) by the cam (222), depending on the direction of rotation; - the camshaft (225) or a lever (220) on the camshaft (225) has a first dowel pin (223) which extends radially away from the camshaft (225) at a first angular position, and a second dowel pin (223) which extends radially away from the camshaft (225) at a second angular position; - the pressure unit (210) comprises an end stop (224) for the first dowel pin (223) and for the second dowel pin (223) which is designed to limit the rotation of the camshaft (225) to angular positions between the first and the second angular position; - the end stop (224) is removable; - the camshaft (225) is designed to be rotated beyond the second angular position when the end stop (224) is removed; and - the pressure unit (210) is designed such that the cam (222) is moved out of the opening of the fork (214) when the camshaft (225) is rotated beyond the second angular position.

Description

[0001] The invention relates to a pressure unit for a drive roller of a printing device.

[0002] Printing devices, especially inkjet printers, can be used to print on recording media such as paper. For this purpose, one or more printheads, each with one or more nozzles, can be used to fire ink droplets onto the recording media and thus create a desired printed image on the media.

[0003] A printing device can be configured to print on a tape-shaped recording medium. The printing device can then have a drive roller designed to drive the recording medium and move it through the printing mechanism of the printing device, in particular to pull it through the printing mechanism. The recording medium can be arranged between the drive roller and a pressure unit, the pressure unit being designed to press the recording medium against the drive roller to ensure reliable propulsion of the recording medium by means of the drive roller.

[0004] The pressure unit typically includes a flexible pressure roller designed to be pressed against the drive roller. To insert a recording medium into a gap between the pressure roller and the drive roller, the pressure unit can be pivoted away from the drive roller. Furthermore, it may be necessary to replace the pressure roller due to wear. For this purpose, the pressure unit can be pivoted further away from the drive roller.

[0005] This document addresses the technical problem of providing a pressure unit for a drive roller for driving a recording medium, which can be pivoted into different positions or states in a convenient, reliable, and safe manner (in particular for inserting a recording medium or for replacing the pressure roller of the pressure unit). This problem is solved by the features of independent device claim 1.

[0006] According to one aspect of the invention, a pressure unit for a drive unit for driving a web-shaped recording medium is described. The drive unit can have a drive roller which is driven by an electric motor. The pressure unit can be configured to press a recording medium arranged between the pressure unit and the drive roller against the drive roller in order to ensure reliable driving of the recording medium by the drive roller across its entire width.

[0007] The pressure unit comprises a pivoting arm with a pressure roller. The pivoting arm is designed to pivot away from the drive roller of the drive unit along a main axis of rotation, or conversely, to pivot towards the drive roller of the drive unit. As a result, the gap between the pressure roller and the drive roller can be increased or decreased.

[0008] The pressure unit further comprises a fork arranged on the pivot arm, the fork having, for example, two tines that enclose an opening of the fork. The fork can be arranged along the longitudinal axis of the pivot arm, which extends from the main axis of rotation along the length of the pivot arm, at the end of the pivot arm furthest from the main axis of rotation. Furthermore, the opening of the fork can be oriented away from the main axis of rotation.

[0009] Furthermore, the pressure unit comprises a camshaft with a cam. The camshaft can be arranged in front of the end of the pivot arm furthest from the main axis of rotation. In particular, the camshaft can be arranged at, in, or in front of the opening of the fork. The camshaft can be designed to rotate about a shaft axis of rotation. This shaft axis of rotation can be parallel to the main axis of rotation. Furthermore, the shaft axis of rotation and the main axis of rotation can be arranged at opposite ends of the pressure unit, in particular of the complete arm consisting of the pivot arm and fork.

[0010] The camshaft can be designed to rotate while the cam is positioned in the opening of the fork. As the camshaft rotates, the cam can then act on the fork, particularly on a prong of the fork, so that, depending on the direction of rotation, the pivot arm is swung away from or towards the drive roller of the drive unit. In particular, a rotation in a second direction, e.g., counterclockwise, can cause the cam to act on the prong of the fork facing the drive roller, thus moving the pivot arm with the pressure roller towards the drive roller. Furthermore, a rotation in the opposite direction, e.g.,clockwise, this causes the cam to act on the tine of the fork that is facing away from the drive roller, so that the pivot arm with the pressure roller is moved away from the drive roller.

[0011] This describes a pressure unit comprising a pressure roller mounted on a pivot arm, the pivot arm being pivotable about a main axis of rotation and having a fork at the end of the pivot arm furthest from the main axis of rotation. The pressure unit further comprises a camshaft with a cam that can be located in the opening of the fork of the pivot arm, and which is configured to move the pivot arm away from the drive roller by rotating the camshaft in the first direction, thus creating an insertion gap between the pressure roller and the drive roller. The insertion gap can be sufficiently wide, e.g., between 3 mm and 6 mm, to allow a user to insert a recording medium between the pressure roller and the drive roller.The cam can further be designed to move the pivot arm towards the drive roller by rotating the camshaft in the second direction, in order to press the pressure roller against the drive roller. In this way, a recording medium arranged between the pressure roller and the drive roller can be reliably driven by the drive roller.

[0012] The provision of a camshaft that engages in the fork of a pivot arm of the pressure unit makes it possible to move the pressure roller in a convenient and reliable manner into different positions, in particular to enable the safe threading of a recording medium and / or to enable a reliable drive of the recording medium and / or to enable convenient maintenance of the pressure roller.

[0013] The pressure unit can also have a lever on the camshaft, allowing the user to rotate the camshaft by hand. This enables particularly convenient positioning of the pressure roller.

[0014] The camshaft or the lever on the camshaft can have a first dowel pin that extends radially away from the camshaft at a first angular position. Furthermore, the camshaft or the lever on the camshaft can have a second dowel pin that extends radially away from the camshaft at a second angular position. The angle between the first and second angular positions can be, for example, between 180° and 230°.

[0015] The pressure unit can include an end stop, in particular a common end stop, for the first and second dowel pins, designed to limit the rotation of the camshaft to angular positions between the first and second angular positions. The provision of dowel pins and an end stop enables particularly convenient, reliable, and precise adjustment of the pressure roller.

[0016] In particular, the pressure unit can be designed such that it is in a pressure state, in which the pressure roller is pressed against the drive roller, especially with a defined pressure, when the first locating pin touches the end stop and / or when the camshaft is in the first angular position. Furthermore, the pressure unit can be designed such that it is in a threading state, in which a threading gap for threading a recording medium is formed between the pressure roller and the drive roller when the second locating pin touches the end stop and / or when the camshaft is in the second angular position. The rotation of the camshaft thus enables particularly convenient and reliable positioning of the pressure roller.

[0017] The end stop can be removable. Furthermore, the camshaft can be designed to rotate beyond the second angular position when the end stop is removed. Removing the end stop thus allows for a deliberate further rotation of the camshaft beyond the second angular position, particularly to facilitate the transfer of the pressure unit into a maintenance state, such as for replacing the pressure roller.

[0018] The pressure unit can be designed such that the cam is moved out of the fork opening when the camshaft is rotated beyond the second angular position. Removing the cam from the fork opening allows a user of the pressure unit to raise the pivot arm to access the pressure roller.

[0019] The camshaft may include a release lever configured to act on a tine of the fork, particularly the tine facing the drive roller, to lift the fork when the camshaft is rotated further beyond the second angular position after the cam has moved out of the fork opening. The tine of the fork may have a pin. Furthermore, the release lever may have a hook configured to at least partially engage the pin of the tine of the fork to lift the fork. This ensures, with particular reliability, that the pivot arm is raised further by rotating the camshaft beyond the second angular position to further increase the gap between the pressure roller and the drive roller.

[0020] The pressure unit can be designed in such a way that, by rotating the camshaft beyond the second angular position, the pressure unit is moved into a maintenance state in which the pivoting of the swivel arm around the main axis of rotation in a direction away from the drive roller is no longer blocked by the cam of the camshaft. This allows a user of the pressure unit to safely pivot the swivel arm away from the drive roller by hand to gain access to the pressure roller.

[0021] The fork can be movably arranged on the pivot arm such that the combined arm, consisting of the fork and pivot arm, is compressible along its longitudinal axis. This can be achieved, in particular, by at least one guide slot extending along the longitudinal axis, e.g., on the fork, and by a guide pin movably arranged therein, e.g., attached to the pivot arm. Furthermore, a spring, e.g., attached at one end to the fork and at the other to the guide pin, can be used to extend the combined arm along its longitudinal axis when no compressive force acts on the fork. Providing a compressible combined arm enables a particularly reliable transition of the pressure unit into its various states.In particular, it is possible to compress the entire arm as the cam rotates, through the action of the cam on the fork, thus rotating the camshaft relative to the end stop from the first angular position to the second. This enables a reliable transition from the compressed state to the threaded state. Furthermore, this ensures that the camshaft is held stably in the different states, especially in the compressed and threaded states, since force is required to compress the entire arm to move it between them.

[0022] The pressure unit can therefore be designed in such a way that, by rotating the camshaft in the first direction of rotation, the pressure unit can be moved from the pressure state, in which the pressure roller is pressed against the drive roller, via the threading state, in which a threading gap for threading a recording medium is arranged between the pressure roller and the drive roller, to the maintenance state, in which the swivel arm with the pressure roller can be swung away from the drive roller by a user of the pressure unit by hand.

[0023] Furthermore, the pressure unit can be designed in such a way that by rotating the camshaft in the opposite second direction of rotation, the pressure unit can be transferred from the maintenance state, via the threading state, to the pressure state.

[0024] This makes it possible to bring about different states of the pressure unit in a convenient and safe manner by simply rotating the camshaft.

[0025] According to another aspect, a drive unit for a recording medium is described, which includes the pressure unit and a drive roller described in this document.

[0026] According to another aspect, a printing device is described which includes the drive unit described in this document.

[0027] Exemplary embodiments of the invention will now be described in more detail with reference to the schematic drawing. These show: Fig. 1 a block diagram of an exemplary inkjet printing device; Fig. 2a to 2c different views of a printing unit in a printing state; Fig. 2d an exemplary camshaft in a side view; Fig. 3a to 3b different views of the pressure unit in a threading state for threading a recording medium; Fig. 4a to 4c different positions of the pressure unit when transferring the pressure unit to a maintenance state; and Fig. 5a to 5c different positions of the pressure unit when transferring the pressure unit into the pressure state.

[0028] The in Fig. The printing device 100 shown in Figure 1 is designed for printing onto a tape-shaped recording medium 120. The recording medium 120 can be made of paper, cardboard, carton, metal, plastic, textiles, a combination thereof, and / or other suitable and printable materials. The recording medium 120 is guided through the printing unit 140 of the printing device 100 along the transport direction 1, indicated by an arrow. Fig. Figure 1 shows an example of an inkjet printing device. It should be noted that the aspects described in this document are also applicable to other types of printing devices, e.g., toner printing devices.

[0029] In the illustrated example, the printing unit 140 of the printing device 100 comprises two printing bars 102, each printing bar 102 being usable for printing with ink of a specific color, e.g., black, cyan, magenta, and / or yellow, and optionally MICR ink. Different printing bars 102 can be used for printing with different inks. Furthermore, the printing device 100 typically includes at least one fixing or drying unit configured to fix a printed image printed onto the recording medium 120.

[0030] A print bar 102 can comprise one or more print heads 103, which may be arranged side by side in several rows to print the pixels of different columns 31, 32 of a print image onto the recording medium 120. In the Fig. In the example shown, a print bar 102 comprises five print heads 103, each print head 103 printing the pixels of a group of columns 31, 32 of a print image onto the recording medium 120.

[0031] Each printhead 103 of the printing unit 140 comprises in the Fig. In the embodiment shown in Figure 1, several nozzles 21, 22 are provided, each nozzle 21, 22 being configured to fire or propel ink droplets onto the recording medium 120. For example, a printhead 103 of the printing unit 140 can comprise several thousand effectively used nozzles 21, 22 arranged along several rows transverse to the transport direction 1 of the recording medium 120. By means of the nozzles 21, 22 of a printhead 103 of the printing unit 140, pixels of a line of a printed image can be printed onto the recording medium 120 transverse to the transport direction 1, i.e., along the width of the recording medium 120.

[0032] The printing device 100 further comprises a control unit 101, e.g., control hardware and / or a controller, which is configured to control the actuators of the individual nozzles 21, 22 of the individual printheads 103 of the printing unit 140 in order to apply the printed image to the recording medium 120 depending on print data. The print data can indicate for each nozzle 21, 22, i.e., for each column 31, 32 of the printed image, and for each line of the printed image, whether ink should be ejected or not, and if so, what quantity of ink should be ejected.

[0033] The printing unit 140 of the printing device 100 thus comprises at least one printing bar 102 with K nozzles 21, 22, which can be controlled with a specific line rate to print a line, running perpendicular to the transport direction 1 of the recording medium 120, with K pixels or K columns 31, 32 of a printed image onto the recording medium 120, e.g. with K>1000. In the illustrated example, the nozzles 21, 22 are fixed in the printing device 100, and the recording medium 120 is moved past the stationary nozzles 21, 22 at a specific transport speed.

[0034] The printing device 100 may further comprise a drive unit 150 which is configured to convey, in particular to pull, a recording medium 120 to be printed through the printing unit 140 of the printing device 100.

[0035] Fig. Figures 2a to 2c show different views or sections of a drive unit 150, which includes a drive roller 200, driven, for example, by an electric motor. Furthermore, the drive unit 150 includes a pressure unit 210, which includes a pressure roller 212 and is configured to clamp a recording medium 120 arranged between the pressure roller 212 and the drive roller 200 in such a way that the recording medium 120 can be moved by the drive roller 200.

[0036] In particular, it shows Fig. 2a the drive unit 150 in a view perpendicular to a rotation axis of the drive roller 200 and / or the pressure roller 212. Fig. Figure 2b shows a section through the drive unit 150 to reveal a cam 222 of a camshaft 225 of the pressure unit 210. Fig. Figure 2c shows a section through the drive unit 150 to reveal a release lever 242 of the camshaft 225 of the pressure unit 210.

[0037] Fig. Figure 2d shows the camshaft 225 of the pressure unit 210 in a side view, where the camshaft runs transversely from left to right across the image plane. The camshaft 225 can have an operating lever 220, a cam 222, and a release lever 242.

[0038] Fig. 3a and Fig. Figure 3b shows different sections through the drive unit 150, which is in the threading state. Fig. Figures 4a to 4c show sections through the drive unit 150 during a transition from the threading state to the maintenance state. Fig. Figures 5a to 5c show sections through the drive unit 150 during a transition from the maintenance state to the pressure state.

[0039] The pressure unit 210 comprises a pivot arm 213, which is designed to pivot about a main axis of rotation 211 of the pressure unit 210. A fork 214 is arranged on the pivot arm 213, extending the pivot arm 213 on a side facing away from the main axis of rotation 211. The fork 214 is mounted on the pivot arm 213 such that the overall length of the arm, consisting of the pivot arm 213 and the fork 214, is variable. In particular, the fork 214 can have one or more guide slots 215 extending longitudinally along the arm. A guide pin 216, attached to the pivot arm 213, can be arranged in each guide slot 215, so that the guide pin 216 slides in the respective guide slot 215 when the arm is lengthened or shortened.A spring 217, in particular a coil spring, can be arranged on at least one guide pin 216, which is attached on one side to the fork 214 and on the other side to the guide pin 216, and which is designed to pull or push the fork 214 away from the main axis of rotation 211 in order to increase the length of the overall arm, in particular to ensure that the overall arm has a maximum possible length when no compressive force acts on the fork 214.

[0040] The fork 214 has an opening at the end furthest from the main axis of rotation 211, in which the camshaft 225 with a cam 222 is arranged, the camshaft 225 being rotatable about a shaft axis of rotation 221 that runs parallel to the main axis of rotation 211. A lever 220 can be attached to the camshaft 225, which allows a user of the pressure unit 210 to rotate the camshaft 225. One or more dowel pins 223 can be arranged on the lever 220, each configured to abut against an end stop 224, so that the angular range of rotation of the camshaft 225 is limited by the one or more, in particular by two, dowel pins 223, e.g. to 220° or less.

[0041] The cam 222 on the camshaft 225 can be designed such that the cam 222 projects into the opening of the fork 214, and presses the fork 214, and thus also the entire arm with the pressure roller 212 of the pressure unit 210, against the drive roller 200. This position of the cam 222 can be achieved, for example, by rotating the camshaft 225 in a second direction, e.g., counterclockwise, until a first dowel pin 223 contacts the end stop 224, as shown in Fig. 2a shown. The pressure unit 210 is then in a pressure state for driving a recording medium 120.

[0042] On the other hand, by rotating the lever 220 or the camshaft 225, the following can be done: Fig. The first direction shown in 2a causes the cam 222 to lift the fork 214 and thus also the entire arm with the pressure roller 212 from the drive roller 200.

[0043] The lever 220 can be rotated such that a second dowel pin 223 touches the end stop 224, as shown in Fig. Figure 3a shows that the pressure unit 210 is in a threading state, in which there is a sufficiently large gap between the pressure roller 212 and the drive roller 200, e.g., 6 mm or less, to allow a user of the printing device 100 to thread a recording medium 120 into or out of the gap between the pressure roller 212 and the drive roller 200. Fig. As can be seen in 3a, the expression lever 242 can cause the entire arm to be partially compressed along the longitudinal direction of the entire arm in the threading state.

[0044] The end stop 224 can be designed to be removed from the pressure unit 210 to allow a user, in particular a maintenance person, to move the lever 220 further along the Fig. 3a to turn in the first direction shown in order to transfer the pressure unit 210 from the threading state to a maintenance state in which it is possible to replace the pressure roller 212.

[0045] A release lever 242 can be arranged on the camshaft 225, which is fixedly connected to the camshaft 225 and thus rotates together with the camshaft 225. A hook 241 can be arranged on the release lever 242, which engages in the Fig. 3a shows the first direction of rotation moving towards a release pin 251 on a prong of the fork 214, see Fig. 3b. As the rotation of the camshaft 225 continues, the hook 241 engages the release pin 251, so that the fork 214 and thus the entire arm with the pressure roller 212 are moved further away from the drive roller 200 by the release lever 242.

[0046] The transition of the pressure unit 210 from the threading state to the maintenance state is described in the Fig. Figures 4a to 4c illustrate this. The entire arm is compressed longitudinally during the transfer. In the maintenance state, the gap between the pressure roller 212 and the drive roller 200 is sufficiently large, in particular 120 mm or more, to allow a maintenance person to replace the pressure roller 212. In this maintenance state, the hook 241 of the release lever 242 may be separated from the release pin 251, and the cam 222 may be positioned outside the opening of the fork 214, as shown in Fig. 4c is shown so that a maintenance person can further raise the entire arm by hand, making the pressure roller 212 even more accessible.

[0047] Fig. Figures 5a to 5c illustrate how the pressure unit 210 is operated by turning the lever 220, which is not in the Fig. 5a to 5c is shown, into which in Fig. The second direction shown in Figure 5a allows the cam to be moved from the maintenance state to the pressure state. In this process, the cam 222 is rotated back into the opening of the fork 214 until the fork 214 is finally pressed against the drive roller 200 by the cam 222.

[0048] A pressure unit 210 is thus described, which is designed to press a ribbon-shaped recording medium 120 against the drive roller 200 with a defined force in the pressure state. The defined force is determined by the position of the cam 222 in the pressure state. The pressure is applied uniformly across the entire width of the recording medium 120 to ensure stable and straight web tracking of the recording medium 120.

[0049] The pressure roller 212 is typically elastic to allow the recording medium 120 to pass gently through the nip, defined by the pressure roller 212 and the drive roller 200. Due to its soft composition, the pressure roller 212 is subject to relatively high wear and therefore needs to be replaced regularly. A convenient and safe replacement of the pressure roller 212 is made possible by the maintenance status of the pressure unit 210.

[0050] The pressure unit 210 described in this document comprises a pivoting unit or pivoting arm 213, which is configured to accommodate the pressure roller 212. Furthermore, the pressure unit 210 comprises a stationary camshaft 225 with a cam 222, which is configured to control the movement of the pivoting unit 213.

[0051] For the two operating positions, i.e., the pressure state and the threading state, both assemblies, i.e., the pivoting unit 213 and the camshaft 225, are coupled together. The cam 222 of the camshaft 225 is positioned in the fork 214 of the pivoting unit 213, with the fork 214 being mounted on the pivoting unit 213. Rotary movements of the camshaft 225 are thus transmitted to a relatively small angular movement of the pivoting unit 213. In the threading state, the opening angle of the pivoting unit 213 relative to the drive roller 200 is preferably so small, e.g., 6 mm or less, that no part of a user's body can be drawn into the gap between the pressure roller 212 and the drive roller 200.

[0052] The change from the threading state to the maintenance state can be accomplished by pivoting the pressure unit 210, in particular the pivoting unit 213. For this purpose, the end stop 224 for the camshaft 225 is removed. The rotation of the camshaft 225 can then continue. The release lever 242, which is located on the camshaft 225, pushes the fork 214 of the pressure unit 210 away from the cam 222 of the camshaft 225. As the camshaft 225 continues to rotate, the fork 214 of the pressure unit 210 is lifted over the cam 222 of the camshaft 225. After a further rotation of the camshaft 225, e.g., by 200° or more, the pressure unit 210, in particular the pivoting unit 213, is completely decoupled from the camshaft 225. A spring 217 pushes the fork 214 back into the extended zero position after the decoupling is complete.

[0053] The release lever 242 has a receptacle 241, in particular a hook, for the fork 214, in particular for a pin 251 of the fork 214, for the decoupling and coupling processes. With the rotation of the camshaft 225 in the second direction of rotation, with the end stop 224 removed, the fork 214 can be lifted onto the cam 222 to engage the fork 214 and the pivoting unit 213 in the camshaft 225. With the rotation of the camshaft 225 in the first direction of rotation, with the end stop 224 removed, the fork 214 can be lifted over the cam 222 to decouple the fork 214 and the pivoting unit 213 from the camshaft 225.

[0054] The measures described in this document enable a clear separation between the two operating states, i.e., the pressure state and the threading state, on the one hand, and the maintenance state, on the other. Furthermore, they ensure that no gap exists when the pressure unit 210 is pivoted into a retracted position, thus preventing a user from being trapped. The pivoting unit 213 with the pressure roller 212 is easily separated from the camshaft 225 by rotating the camshaft 225. Once the two units, i.e., the pivoting unit 213 and the camshaft 225, are separated, the pivoting unit 213 can be moved into the maintenance state with a simple pivoting motion.

[0055] This document describes a pressure unit 210 configured to press a pressure roller 212 against a drive roller 200. Furthermore, this document describes a drive unit 150 for a recording medium 120, comprising a pressure unit 210 and a drive roller 200. Finally, this document describes a printing device 100 comprising the drive unit 150 described herein. Reference symbol list 1. Transport direction 21, 22 Nozzle (print pattern) Columns 31 and 32 (of the printed image) 100 printing device 101 Control unit 102 pressure bars 103 Printhead 120 recording media 140 printed works 150 drive unit 200 drive roller 210 pressure unit 211 Main axis of rotation 212 Pressure roller 213 Swivel arm 214 Fork (on the swivel arm) 215 guide slots 216 guide pins 217 spring 220 operating levers 221 Shaft rotation axis 222 cams (camshaft) 223 Dowel pin 224 End stop 225 camshaft 241 hooks 242 Release lever 251 pin

Claims

[1] Pressure unit (210) for a drive unit (150) for driving a web-shaped recording medium (120); wherein the pressure unit (210) comprises, - a pivoting arm (213) with a pressure roller (212), wherein the pivoting arm (213) is designed to pivot a main axis of rotation (211) away from or towards a drive roller (200) of the drive unit (150), so that a gap between the pressure roller (212) and the drive roller (200) is increased or decreased; - a fork (214) arranged on the swivel arm (213); - a camshaft (225) with a cam (222), wherein the camshaft (225) is designed to be rotated about a shaft axis of rotation (221), while the cam (222) is arranged in an opening of the fork (214), so that when the camshaft (225) is rotated, the pivot arm (213) is pivoted away from or towards the drive roller (200) of the drive unit (150) by the cam (222), depending on the direction of rotation; - the camshaft (225) or a lever (220) on the camshaft (225) has a first dowel pin (223) which extends radially away from the camshaft (225) at a first angular position, and a second dowel pin (223) which extends radially away from the camshaft (225) at a second angular position; - the pressure unit (210) comprises an end stop (224) for the first dowel pin (223) and for the second dowel pin (223) which is designed to limit the rotation of the camshaft (225) to angular positions between the first and the second angular position; - the end stop (224) is removable; - the camshaft (225) is designed to be rotated beyond the second angular position when the end stop (224) is removed; and - the pressure unit (210) is designed such that the cam (222) is moved out of the opening of the fork (214) when the camshaft (225) is rotated beyond the second angular position. [2] Pressure unit (210) according to claim 1, wherein the pressure unit (210) comprises a lever (220) on the camshaft (225) which enables a user to rotate the camshaft (225) with one hand. [3] Pressure unit (210) according to claim 1 or 2, wherein the pressure unit (210) is designed such that - that the pressure unit (210) is in a pressure state in which the pressure roller (212) is pressed against the drive roller (200) when the first dowel pin (223) touches the end stop (224) and / or when the camshaft (225) is in the first angular position; and - that the pressure unit (210) is in a threading state in which a gap is formed between the pressure roller (212) and the drive roller (200) for threading a recording medium (120) when the second locating pin (223) touches the end stop (224) and / or when the camshaft (225) is in the second angular position. [4] Pressure unit (210) according to one of the preceding claims, wherein - the camshaft (225) includes a release lever (242) configured to act on a prong of the fork (214) to lift the fork (214) when the camshaft (225) is rotated further beyond the second angular position after the cam (222) has been moved out of the opening of the fork (214); and the pressure unit (210) is configured in particular such that by rotating the camshaft (225) beyond the second angular position, the pressure unit (210) is brought into a maintenance state in which pivoting of the pivot arm (213) about the main axis of rotation (211) in a direction of rotation away from the drive roller (200) is no longer blocked by the cam (222) of the camshaft (225). [5] Pressure unit (210) according to claim 4, wherein - the tine of the fork (214) has a pin (251); and - the release lever (242) has a hook (241) designed to at least partially enclose the pin (251) of the prong of the fork (214) in order to lift the fork (214). [6] Pressure unit (210) according to one of the preceding claims, wherein - the fork (214) is arranged along a longitudinal axis of the swivel arm (213) at an end of the swivel arm (213) facing away from the main axis of rotation (211); and / or - the opening of the fork (214) is aligned away from the main axis of rotation (211). [7] Pressure unit (210) according to claim 6, wherein the fork (214) is movably arranged on the pivot arm (213), in particular by means of at least one guide slot (215) extending along the longitudinal axis and a guide pin (216) movably arranged therein, such that an overall arm consisting of fork (214) and pivot arm (213) can be compressed when the camshaft (225) is rotated along the longitudinal axis. [8] Pressure unit (210) according to one of the preceding claims, wherein - the pressure unit (210) is designed such that by rotating the camshaft (225) in a first direction of rotation, -- the pressure unit (210) starting from a pressure state in which the pressure roller (212) is pressed against the drive roller (200), -- via a threading state in which a gap is arranged between the pressure roller (212) and the drive roller (200) for threading a recording medium (120), -- can be brought into a maintenance state in which the swivel arm (213) with the pressure roller (212) can be swivelled away from the drive roller (200) by a user of the pressure unit (210) with one hand; and - the pressure unit (210) is designed such that by rotating the camshaft (225) in an opposite second direction of rotation, the pressure unit (210) can be transferred from the maintenance state, via the threading state, to the pressure state.

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