阅读说明：本技术 可移动的压板肋 (Movable pressure plate rib ) 是由 W·H·托 韦斯利·谢 王旭刚 W·L·泰奥 于 2017-04-17 设计创作，主要内容包括：描述一种具有可移动的压板肋(110、112)的装置(102)。该装置包括用以支撑打印介质(106)的压板(108)。压板在打印介质被传送用以打印的平面中延伸。该装置进一步包括第一组压板肋(110)和第二组压板肋(112),每个被安装在压板上。第二组压板肋能大致垂直于该平面移动。(An apparatus (102) having movable platen ribs (110, 112) is described. The apparatus includes a platen (108) to support a print medium (106). The platen extends in a plane in which the print medium is conveyed for printing. The apparatus further includes a first set of platen ribs (110) and a second set of platen ribs (112), each mounted on the platen. The second set of platen ribs can move substantially perpendicular to the plane.)

1. An apparatus, comprising:

a platen to support a print medium, wherein the platen extends in a plane in which the print medium is conveyed for printing; and

a first set of platen ribs and a second set of platen ribs, each set of platen ribs being mounted on the platen, wherein the second set of platen ribs is movable substantially perpendicular to the plane.

2. The apparatus of claim 1, comprising a print head and a control engine in communication with the second set of platen ribs, wherein the control engine is to:

obtaining a value of a print-related parameter corresponding to a printing operation;

determining, based on the value of the print-related parameter, an occurrence of a physical change in the print medium during the printing operation; and

based on the determination, a control signal is generated to actuate any of the second set of platen ribs to control a spacing between the print medium and the printhead.

3. The apparatus of claim 1, wherein each of the second set of platen ribs is to support a portion proximate an edge of the print medium.

4. The apparatus according to claim 1, wherein the print-related parameter includes an attribute related to one of print jobs corresponding to the printing operation and a physical characteristic of the print medium.

5. The apparatus of claim 4, wherein the attributes associated with the print job include ink density at which content is printed on the print medium.

6. The device of claim 2, comprising an actuation mechanism coupled to the control engine, wherein the actuation mechanism is to:

receiving a control instruction generated by the control engine; and

based on the control command, actuating one of the second set of platen ribs.

7. The device of claim 6, wherein the actuation mechanism comprises a cam-linkage mechanism.

8. The apparatus of claim 1, wherein the first set of platen ribs and the second set of platen ribs are arranged in series, wherein the first set of platen ribs is arranged in the middle of the second set of platen ribs.

9. The apparatus of claim 2, wherein to determine the occurrence of the physical change, the control engine is further to:

comparing the value to mapping data, wherein the mapping data associates the value with an indication that the print medium is likely to undergo the physical change; and

if the value matches the mapping data, determining that the physical change occurred.

10. The apparatus of claim 1, wherein each of the second set of platen ribs has a different size.

11. A method, comprising:

obtaining a value of a print-related parameter corresponding to a printing operation;

processing the values to determine a likelihood of a physical change to the print medium during the printing operation; and

controlling movement of a movable platen rib of a set of movable platen ribs based on the likelihood of the physical change occurring.

12. The method of claim 11, wherein the print-related parameters include an attribute related to one of the print jobs corresponding to the printing operation and a physical characteristic of the print medium.

13. The method of claim 12, wherein an attribute comprises a physical characteristic of the print medium.

14. The method of claim 11, wherein the controlling comprises one of:

lowering the set of movable platen ribs upon determining that the print media is likely to undergo the physical change; and

raising the set of movable platen ribs upon determining that the print medium is unlikely to undergo the physical change.

15. A non-transitory computer readable medium comprising instructions executable by a processing resource to:

obtaining a value of a print-related parameter corresponding to a printing operation;

processing the values to determine a likelihood of a physical change to the print medium during the printing operation; and

based on the likelihood of the physical change occurring, a control signal is generated to affect and control movement of the movable platen rib between the raised and lowered positions.

Background

In general, printing operations in inkjet-based printing devices and apparatus include moving a print medium relative to a printhead. The printhead ejects a predetermined amount of ink from its nozzles onto a print medium to form characters, which form print on the print medium. During a printing operation, the print medium is supported by the platen. The protrusions on the platen, referred to as platen ribs, maintain the spacing distance between the printhead and the print media. The spacing distance is maintained to avoid positional error of ink droplets or to avoid smudging (smearing) of the nozzles of the printhead to the print medium.

Drawings

The following detailed description refers to the accompanying drawings in which:

FIG. 1 is a schematic view of an example apparatus including a platen and having a set of movable platen ribs;

FIG. 2 is a schematic view of another example apparatus having a set of movable platen ribs to control spacing between a print medium and a printhead;

FIG. 3 depicts a front view of an example platen and a set of raised platen ribs;

FIG. 4 depicts a front view of an example platen and a set of lowered platen ribs;

FIG. 5 depicts a top view of another example platen and a set of movable platen ribs;

6-7 depict perspective views of example platens;

FIG. 8 depicts an example method to control spacing between a print medium and a printhead of a printing device; and

FIG. 9 is a block diagram of an example environment to implement non-transitory computer-readable media to control spacing between print media and a printhead.

Detailed Description

Typically, a printing operation in an inkjet-based device involves moving a print medium relative to a printhead. The print head ejects a predetermined amount of ink from its nozzles onto a print medium to form characters, thereby forming print on the print medium. The separation distance between the print head and the print medium is maintained to achieve the desired print quality. For example, the separation distance may be close enough to prevent positional error of the ink droplets. At the same time, the spacing distance can be kept to a minimum to avoid soiling of the print media by the nozzles of the print head. If the distance is less than such a minimum distance, the print medium may come into contact with the nozzles of the print head, causing an obstruction in the print path and resulting in a jam.

It is also observed that once the ink is deposited, the print medium may undergo some physical change. For example, the print media may curl or bend at its edges as ink is deposited, or may wrinkle. When curled or wrinkled, the separation distance between the print media and the printhead is reduced, which may lead to smudging or jamming of the print media. Cockling may be understood as a planar change, manifested as a crease in the surface of the print medium. Such variations in the otherwise regular surface of the print medium may reduce the separation distance between the printhead and the print medium during printing.

During a printing operation, the print media is supported by a series of platen ribs. Typically, each of such platen ribs may be formed as a plate and rigidly mounted on the platen. The platen ribs are positioned such that a plane in which the platen ribs lie is substantially perpendicular to a surface of the print medium. When the printing medium is conveyed during printing, the surface of the printing medium is kept in contact with the edge of the platen rib. The platen ribs may be arranged in series with adjacent platen ribs being spaced apart by a specified distance. Typically, the height of the platen ribs varies. For example, when some platen ribs and other platen ribs that contact portions of the print medium around the edges extend from the surface of the platen, the some platen ribs may be shorter than the other platen ribs. The shorter platen ribs serve to offset any curl that may occur at the edges of the print media. In such a case, since the platen rib is short, the distance between the print head and the print medium remains constant even though the print medium may have curled toward the print head.

During the printing process, the print medium may not always curl. In this case, the depressed ribs may cause an increase in the spacing distance between the print head and the printing medium. This increase in separation distance may reduce print quality at the edge of the print medium. Examples include changes in contrast, increases in graininess, and blurring of print near the edges of the print medium.

An apparatus having a movable set of platen ribs is described. The present specification also describes a method of controlling the separation distance between the print media and the printhead of such a device by the set of movable platen ribs. In one example, the apparatus may include a platen to which the first set of platen ribs and the second set of platen ribs are mounted. The first set of platen ribs may be positioned such that they support a central portion of the print media. The first set of platen ribs is rigidly mounted to the platen. The second set of platen ribs are positioned such that they correspond to portions located near an edge or corner of the print medium. The platen ribs may be formed as plates extending generally perpendicular to the platen surface.

The second set of platen ribs may be movable in the plane in which they lie. Each of the second set of platen ribs is movable between one or more positions, between a fully raised position and a fully lowered position. In one example, when the second set of platen ribs is fully extended in the raised position, its edges are aligned with the edges of the rigidly fixed first set of platen ribs. In the lowered position, the height of the second set of platen ribs is less than the height of the first set of platen ribs relative to the platen. The second set of platen ribs controls the separation distance between the print media and the printhead of the device. In one example, each of the second set of platen ribs may be independently movable or may be jointly movable without departing from the scope of the present subject matter. In another example, the second set of platen ribs may even be grouped into segments. Each segment of the platen rib may move independently or in unison with respect to one another.

In operation, values of print-related parameters for a printing operation may be obtained. The print-related parameters may include attributes corresponding to the executed print job or physical characteristics of the print medium. Examples of attributes related to a print job may include, but are not limited to, ink density; physical properties of the print medium such as size, weight, and rigidity. The print-related parameters may be considered to be conditions that exist during the printing operation that may cause physical effects (such as curling) of the print medium. It should be noted that physical effects refer to changes in the physical properties of the print medium, which will result in variations between the otherwise regular surfaces of the print medium. Other examples of print-related parameters may also be relied upon without departing from the scope of the claimed subject matter.

Returning to the operation of the apparatus, once the value of the print-related parameter is obtained, the possibility of any physical effect occurring on the print medium is judged. In one example, the determination may be based on a value of a print-related parameter. From the respective values of the print-related parameters it can be concluded that a physical effect of the print medium may occur. Based on this determination, one or more control instructions may be generated. Such control instructions, when executed, may further actuate the actuation mechanism to raise or lower the second set of platen ribs. In one example, if it is determined that the print media is likely to curl, the control engine may lower the set of platen ribs. On the other hand, if it is determined that the print medium is unlikely to curl, the set of platen ribs may be raised to maintain a certain spacing distance between the print medium and the printhead. Examples of such actuation mechanisms include, but are not limited to, cam and linkage systems.

It is to be appreciated that the present subject matter can control the spacing between the print media and the printhead by assessing whether the print media is likely to curl. Thus, a set of platen ribs can be raised or lowered, thereby preventing print-related artifacts and improving the overall print quality of the printed output. In another example, the dimensions of the second set of platen ribs may also be unequal. In such an example, since each of the platen ribs is different in size when lowered, relative variation may occur between each of the second set of platen ribs. The method can be further implemented using well-known less complex mechanisms.

These and other aspects are described in connection with various examples as shown in fig. 1-8. The present description provides a printing apparatus that may have a print carriage assembly. However, the scope of the present subject matter may not be limited to such a printing apparatus. Other types of devices may also be included within the scope of the present subject matter without limitation. Moreover, in some of the figures, various components that are not sought to be protected are shown using dashed lines.

Fig. 1 shows an apparatus 102 to control the spacing between a print medium and a printhead. The device 102 may be implemented as a printing device. The printing device may include a printer or other multi-function device that may perform other functions such as scanning in addition to printing. In this example, the apparatus 102 may include a printhead 104. The printhead 104 may include one or more nozzles through which a predetermined amount of ink is ejected and deposited onto the print medium 106 to form print. During a printing operation, the print medium 106 is supported on a platen 108. The platen 108 may further be provided with a first set of platen ribs 110-1, 110-2, …, 110-N (referred to as platen ribs 110) and a second set of platen ribs 112-1, 112-2, …, 112-N (referred to as platen ribs 112). The platen ribs 110 may be formed as plates extending in a substantially perpendicular direction from the surface of the platen 108. During a printing operation, as the print media 106 is conveyed through a print path in the device 102, the print media 106 is supported by platen ribs 110 and 112.

Of the platen ribs 110 and 112, a first set of platen ribs 110 is rigidly mounted to the platen 108. The second set of platen ribs 112 also extend generally perpendicular to the surface and are movable relative to the platen 108 (as indicated in FIG. 1). In one example, each of the second set of platen ribs 112 may be movable between a raised position and a lowered position. In the raised position, the height of the second set of platen ribs 112 is equivalent to and substantially equal to the height of the first set of platen ribs 110. Accordingly, in the lowered position, the height of the second set of platen ribs 112 is less than the height of the first set of platen ribs 110.

The second set of platen ribs 112 are positioned such that they support corners or edges of the print media 106. During a printing operation, the second set of platen ribs 112 may move between a raised position and a lowered position depending on whether the print media 106 is undergoing any physical changes that may reduce the overall separation distance between the printhead 104 and the print media 106. If it is determined that the print medium 106 is unlikely to undergo any physical changes, the second set of platen ribs 112 may be fully extended in the raised position such that the furthest edges of the second set of platen ribs 112 are aligned with the edges of the first set of platen ribs 110. Thus, the separation distance between the printhead 104 and the print medium 106 is maintained. On the other hand, if it is determined that the print media 106 may undergo any physical change, one or more of the second set of platen ribs 112 may be lowered. For example, there may be instances where the print media 106 may curl upward toward the printheads 104, thereby reducing the separation distance. In this case, one or more of the second set of platen ribs 112 may be lowered such that the separation distance between the printhead 104 and the print medium 106 is maintained. The second set of platen ribs 112 may be controlled individually or collectively. In one example, the print-related parameters may be used to determine whether any physical changes may occur to the print medium 106 during a printing operation. Thus, the second set of platen ribs 112 may be raised or lowered depending on the value of the print-related parameter.

The apparatus and method described above allow the second set of platen ribs 112 to be raised and lowered to control the spacing between the print media and the printhead. Further, the second set of platen ribs 112 may be raised or lowered according to a print related parameter, which in turn indicates whether the print media 106 may undergo any physical changes. As previously described, this physical change results in a change in the separation distance between printhead 104 and print medium 106. According to one example, the likelihood of physical change may be pre-considered (preempted) and the platen ribs lowered accordingly to ensure that the separation distance is within a prescribed range. This in turn reduces the blurring and graininess of the image, thereby improving the print quality.

These and other examples are provided in more detail in connection with the remaining figures. Fig. 2 illustrates an apparatus 102, which apparatus 102 may be implemented as a printing apparatus in one example. The apparatus 102 as shown in fig. 2 may be implemented by hardware or software using programmable logic. In this example, the apparatus 102 includes an interface 202, a memory 204, and a second set of platen ribs 112 (referred to as platen ribs 112). The interface 202 may include various interfaces, such as interfaces for data input and output devices (referred to as I/O devices), storage devices, network devices, and so forth. The interface 202 facilitates communication between the apparatus 102 and other computing devices connected in a network environment. In one example, the interface 202 may provide an interface for communication between the apparatus 102 and the display unit 202. Memory 204 may store one or more computer readable instructions that may be retrieved and executed to cause an alert to be generated to enable a user to retrieve a printed document. Memory 204 may include any non-transitory computer-readable medium and includes, for example, volatile memory (such as RAM), or non-volatile memory (such as EPROM), flash memory, and so forth. The device 102 further includes an engine 206 and data 208.

The device 102 further includes an actuation mechanism 210. The actuation mechanism 210 may be in communication with any of the engines 206. The actuation mechanism 210 is also mechanically coupled to each of the second set of platen ribs 112. During operation of the device 102, the engine 206 may generate control signals to operate the actuation mechanism 210. Upon receiving the control signal, the actuation mechanism 210 may enable the platen rib 112 to move between the raised position and the lowered position.

The engine 206 may be implemented as a combination of hardware and programming (e.g., programmable instructions) to implement one or more functions of the engine 206. In the examples described herein, this combination of hardware and programming can be implemented in a number of different ways. For example, the programming for the engine 206 may be processor-executable instructions stored on a non-transitory machine-readable storage medium, and the hardware for the engine 206 may include processing resources (e.g., one or more processors) to execute such instructions. In this example, a machine-readable storage medium may store instructions for execution by a processing resource to implement the engine 206. In such examples, the apparatus 102 may include a machine-readable storage medium storing the instructions and a processing resource to execute the instructions, or the machine-readable storage medium may be separate but accessible to the apparatus 102 and the processing resource. In other examples, the engine 206 may be implemented by electronic circuitry.

The data 208 includes data that is predefined or generated as a result of any implemented function in the engine 206. In an example, the engine 206 includes a control engine 212 and other engines 214. The other engines 214 may implement functions to supplement applications or functions performed by the device 102. Further, data 208 may include values of print-related parameters (referred to as parameter values 216), mapping data 218, and other data 220.

As previously described, the second set of platen ribs 112 are movable relative to the platen 108. The platen ribs 112 may move in a direction that is generally orthogonal to the plane of the platen 108. The platen rib 112 may be in a raised position or a lowered position. For example, if print media 106 may experience curl or any other physical change, platen rib 112 may be in a lowered position. Similarly, if it is determined that print media 106 is unlikely to undergo any change, platen rib 112 may be in a raised position. When the platen ribs 112 are in the lowered position, the relative height of the platen ribs 112 is less than the height of the first set of platen ribs 110 (as shown in fig. 1). Conversely, when the platen rib 112 is in the raised position, the height of the platen rib 112 is equivalent or equal to the height of the first set of platen ribs 110.

In one example, the control engine 212 may control movement of the platen rib 112. To do so, control engine 212 may determine one or more values of print-related parameters of the print job (i.e., parameter values 216). A print job may be considered any print operation that must be performed by the apparatus 102 in response to a print command from a user. A print job may generally define content to be printed on print media 106. The instructions from the user may be processed by a computing device (not shown in fig. 2). Such computing device may then send such instructions to the apparatus 102. Based on the instructions, the device 102 determines the manner in which the content is to be rendered (i.e., printed) onto the print medium.

The print-related parameters may be considered to define one or more parameters based on which a printing device, such as the apparatus 102, processes instructions and prints content on the print medium 106. For example, if the content includes areas with darker hues, the corresponding print-related parameter may specify certain values based on which the device 102 determines which type of ink or amount of ink needs to be ejected from the printhead 104. The print-related parameters may also specify the type of print media 106 that must be used to print the desired content. For example, content may have to be printed on a more rigid or possibly larger sized print medium 106. Parameter values 216 may provide one or more values that depict such different conditions that may exist or must be considered in processing a print job.

Continuing with the present example, the device 102 may receive a print command indicating a print job. The control engine 212 may obtain values of print-related parameters from the print commands. The control engine 212 may store the value as the parameter value 216. Based on parameter values 216, control engine 212 may determine whether print media 106 may undergo any physical changes (e.g., curling) during a printing operation. In one example, the control engine 212 may compare the parameter values 216 to the mapping data 218. Mapping data 218 may provide a mapping between one or more parameter values 216 and an indication that print medium 106 may be subject to change. For example, a parameter value 216 indicating a high ink density may be considered a possible condition for curl to occur in the print medium 106. Similarly, the parameter value 216 indicating that a more rigid print medium 106 is being used may be indicated as a condition that does not result in any physical change in the print medium 106. It should be noted that the example of dependence is merely indicative and not limiting. Other examples of parameter values 216 and corresponding conditions may also be used without departing from the scope of the claimed subject matter. In another example, parameter values 216 may be user specified, or may be based on historical or other analysis data.

Once control engine 212 determines the likelihood that any physical changes may occur to print media 106, it may further control platen ribs 112 and move them to positions between the raised and lowered positions. For example, control engine 212 may determine that the ink density is high for the print job under consideration based on parameter values 216. Accordingly, control engine 212 may infer that print medium 106 may curl during a printing operation. The manner in which the platen ribs 112 operate is further explained in conjunction with fig. 3-4. Fig. 3-4 depict different examples of when the platen rib 112 is fully raised (depicted as platen rib 312) and when it is lowered (depicted as platen rib 412).

Returning to the present example, control engine 212 may generate one or more control signals for actuation mechanism 210 upon determining that print medium 106 is unlikely to undergo any physical changes (such as curling). As previously described, the separation distance between the printhead 104 and the print medium 106 does not change without the print medium 106 experiencing any curl. In this case, the control engine 212 may control the platen ribs to be in the raised position (depicted as ribs 312-1, 312-2, …, 312-N). The raised ribs 312 keep their relative height with respect to the platen 108 similar to the height of the first set of platen ribs 110. The control engine 212 may advance and generate control commands to raise the second set of platen ribs 112. The second set of platen ribs 112 continue to move in the direction shown so that they are fully raised (raised ribs 312 as depicted in fig. 3).

It may also be the case that the control engine 212 may determine that the print media 106 may curl during a printing operation. For example, parameter value 216 may indicate that the ink density of the print job under consideration is greater than a threshold value. For high ink densities, control engine 212 may infer that print media 106 may curl upward toward printhead 104. Accordingly, the control engine 212 may generate control signals to lower the selected platen rib 112 from its raised position (as depicted in fig. 4). The platen ribs 112 may be lowered in the direction as shown in fig. 4 such that the relative height of the lowered ribs (i.e., ribs 412-1 and 412-2, collectively ribs 412) is less than the height of the first set of platen ribs 110. In one example, the height to which the ribs 412 are lowered may vary between each of the lowered ribs 412. For example, as shown, even though ribs 412-1 and 412-2 are both lowered, the height of rib 412-1 is different than the height of rib 412-2. The height of the additional ribs 412 may also be different. In this example, the lowering of the ribs 412 is to counter curl of the print media 106. The placement of ribs 412 can maintain an optimal spacing distance between printhead 104 and print medium 106. As described, the present subject matter provides a set of movable platen ribs that can be raised or lowered depending on whether the print media 106 is likely to curl. Anticipating this and raising and lowering the second set of platen ribs 112 accordingly improves print quality.

In an example as depicted in fig. 4, the rib 412 may be further divided into two or more segments. For example, the segments 414-A, 414-B may be positioned such that they are present on either side of the first set of platen ribs 110. In one example, each of the ribs 412 (present in the two segments 414-A, 414-B) may move together. In another example, the motion of segment 414-A may be independent of the motion of segment 414-B. In this case, the actuation mechanism of segment 414-A may be different than the actuation mechanism of segment 414-B without departing from the scope of the present subject matter.

FIG. 5 is a top view of an example platen with rigid and movable platen ribs. The platen 500 includes a first set of platen ribs 110 and a second set of platen ribs 112. The first set of platen ribs 110 are rigidly attached to the platen 500. On the other hand, the second set of platen ribs 112 are movable and may be lowered or raised orthogonally relative to the platen 500. Each of the second set of platen ribs 112 is coupled to the shaft 502 by a connecting rod 504. The connecting rod 504 may be further coupled to a cam device (not shown in fig. 5) of each of the second set of platen ribs 112. The cam device enables each of the second set of platen ribs 112 to reciprocate.

The other end of the shaft 502 is in turn connected to the actuation mechanism 210. The actuating mechanism 210 actuates the second set of platen ribs 112 via the shaft 502. The actuation mechanism 210 may move in a direction as depicted in fig. 5. The actuation mechanism may provide an actuation motion that is transmitted to each of the second set of platen ribs 112 through the shaft 502. The cam device can then lower or raise one or more of the second set of platen ribs 112 accordingly. This example merely indicates the manner in which the second set of platen ribs 112 are actuated. Other mechanisms to actuate the second set of platen ribs 112 are also possible and are within the scope of the claimed subject matter. In this example, each of the second set of platen ribs 112 may move together due to the reciprocating motion imparted by the actuation mechanism 210 through the shaft 502. In another example, each of the second set of platen ribs 112 may be configured such that each of the individual platen ribs 112 moves independently of the other ribs 112. In such an example, each of the second set of platen ribs 112 may be connected to their respective shafts and connecting rods without departing from the scope of the present subject matter.

In another example, the platen 108 may be further provided with one or more ramp profiles coupled with each of the second set of platen ribs 112. A ramp profile (not shown in fig. 5) may be used to define the extent to which any of the second set of platen ribs may be raised. The ramp profile may be used to define one or more presets according to which the respective platen ribs 112 are elevated but at different heights. This example is just one of other possible examples that may be implemented. Other examples are also within the scope of the present subject matter.

In yet another example, each of the second set of platen ribs 112 may have different dimensions instead of implementing a ramp profile that elevates each of the second set of platen ribs 112 to a different degree. Because the dimensions of each of the second set of platen ribs 112 vary, the height of the second set of platen ribs 112 varies between different second sets of platen ribs 112 when lowered.

Fig. 6 and 7 depict perspective views of a platen 600 according to another example of the present subject matter. The platen 600 (as depicted in fig. 6 and 7) illustrates various examples where one or more movable platen ribs may be in a raised position or a lowered position. As depicted in fig. 6-7, the platen 600 includes a plurality of rigidly mounted platen ribs 602 and a plurality of movable platen ribs 604. The movable platen rib 604 may move in a direction perpendicular to the plane of the platen 600. As shown in fig. 6, movable platen ribs 604-1 and 604-3 are in a lowered position. As previously described, movable platen rib 604 may be lowered in the event that it is determined that print media 106 (not shown in fig. 6-7) may undergo a physical change, such as curling or cockling. Each of the movable platen ribs 604 may be raised (as shown in fig. 7) if it is determined that the print medium 106 is unlikely to undergo any physical change. The relative height of the movable platen rib 604 corresponds to the height of the first set of platen ribs 110 when the movable platen rib 604 is in the raised position.

Fig. 8 illustrates an example method 800 implemented in a device having movable platen ribs. According to examples of the present subject matter, a movable platen rib is used to control a spacing distance between a print medium and a printhead. The order in which the method steps are described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the foregoing method, or an alternate method. Further, method 800 may be implemented by any suitable hardware, non-transitory machine readable instructions, or combination thereof, to process a resource or computing device.

At block 802, values of print-related parameters are obtained. In one example, control engine 212 may process the print request to obtain values for the print-related parameters. This value is stored in parameter value 216. As discussed in the preceding paragraph, the print-related parameters may be considered to define one or more parameters based on which the printing device (such as the apparatus 102) processes the instructions and prints the content on the print medium 106. Parameter values 216 may provide one or more values describing these different conditions that may exist or must be considered in processing a print job.

At block 804, the values of the print related parameters are processed to determine a likelihood of a physical change in the print medium. For example, the control engine 212 may compare the parameter values 216 to the mapping data 218. In this example, mapping data 218 may provide a mapping between one or more parameter values 216 and an indication that print medium 106 may be subject to change.

At block 806, based on the value of the print-related parameter, one or more movable platen ribs may be actuated to move between a raised position and a lowered position. For example, based on parameter values 216, control engine 212 may determine whether the coupled second set of platen ribs 112 are to be moved. To this end, control engine 212 may determine whether print medium 106 may undergo any physical changes during a printing operation based on the print-related parameters stored as parameter values 216. In the event that it is determined that print medium 106 will undergo a physical change (such as curl), control engine 212 may further generate one or more control instructions to lower the second set of movable platen ribs 112. Conversely, if it is determined that the print media 106 has not undergone any physical change, the control engine 212 may generate control signals to raise the second set of platen ribs 112.

Fig. 9 illustrates an environment 900 to control a separation distance between a print medium and a printhead of a printing device having a plurality of movable platen ribs according to an example of the present disclosure. The environment 900 may include at least a portion of a public network environment or a private network environment or a combination thereof. In one implementation, the environment 900 includes a processing resource 902 communicatively coupled to a computer-readable medium 904 via a communication link 906.

In one example, the processing resources 902 may include one or more processors of a computing device to generate instructions to move the second set of platen ribs to control a spacing between the print medium and the printhead. In another example, multiple processors may also be used to implement the processing resources 902. For example, computer-readable medium 904 may be an internal storage device or an external storage device of the computing device. In one embodiment, the communication link 906 may be a direct communication link, such as any memory read/write interface. In another embodiment, the communication link 906 may be an indirect communication link, such as a network interface. In this case, the processing resources 902 can access the computer-readable media 904 through the network 908. Network 908 may be a single network or a combination of networks and may use different communication protocols.

The processing resources 902 and computer-readable media 904 may also be coupled to a data source 910 via a communication link 906 and/or to a communication device 912 via a network 908. The coupling to the data source 910 enables data to be received in an offline environment, while the coupling to the communication device 912 enables data to be received in an online environment.

In one implementation, the computer-readable medium 904 includes a set of computer-readable instructions to implement the control module 914. In one example, the instructions implementing the control module 914 may be executable code to move the second set of platen ribs 112. A set of computer readable instructions within the medium 904 may be accessed by the processing resource 902 through the communication link 906 and subsequently executed to process data communicated to the data source 910 in order to control the spacing between the print medium and the print head of the printing apparatus. To this end, the control module 914 controls one or more movable platen ribs of a device (such as device 102).

The apparatus 102 includes a first set of platen ribs 110 and a second set of platen ribs 112, each of the first set of platen ribs 110 and the second set of platen ribs 112 being mounted on a platen 108 (as depicted in fig. 1). The second set of platen ribs 112 are movable relative to the platen 108. The second set of platen ribs 112 may be movable between a fully raised position and a lowered position. As each of the second set of platen ribs 112 moves, their relative height with respect to the first set of platen ribs 110 changes. In operation, the control module 914 may determine the values of one or more print-related parameters. In one example, the value of the print-related parameter may be obtained based on a print request from a user. This value may then be stored in parameter value 216.

Based on the parameter values 216, the control module 914 may determine whether the print medium 106 may undergo any physical changes during the printing operation. For example, the control module 914 may determine, based on the ink density, that the print medium 106 will most likely curl during a printing operation. The control module 914 may compare the parameter values 216 to mapping data 218, which mapping data 218 associates one or more parameter values 216 with possible physical changes that may occur.

In determining whether the print medium 106 will undergo any physical changes, the control module 914 may generate one or more control instructions to affect movement of the second set of platen ribs 112. In this example, such control instructions, when executed, may actuate an actuation mechanism (e.g., actuation mechanism 210) to control the second set of platen ribs 112. If it is determined that the print medium 106 may experience any physical change (e.g., curl), the control instructions, when executed, will raise the second set of platen ribs 112. When the second set of platen ribs 112 are in the raised position, the relative height of the second set of platen ribs 112 is lower than the height of the first set of platen ribs 110. On the other hand, if it is determined that the print medium 106 is unlikely to undergo any physical change, the control instructions cause the level of the second set of platen ribs 112 to be raised when executed.

Although examples of the disclosure have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and are to be construed as examples of the disclosure.