Support structure adjustment

According to one example there is provided a method of adjusting a support structure. The method comprises obtaining a reference orientation of the support structure when the support structure is positioned in a reference position. The height of the support structure is adjusted to a predetermined position and the orientation of the support structure is adjusted such that the orientation of the support structure when in the predetermined position is substantially the same as the reference orientation.

BACKGROUND

In many printing systems the distance between a print engine, and the media which is to be printed on is an important parameter in ensuring high quality printing. In inkjet printing systems, for example, the distance between the lower surface of an inkjet printhead from which drops of printing fluid are ejected, and the top surface of a media is often referred to as the pen to paper spacing (PPS).

Some printing systems enable the height of the print engine to be modified such that an optimal PPS may be maintained when printing on media of different thicknesses.

DETAILED DESCRIPTION

In inkjet printing systems a print engine may comprise one or multiple inkjet printheads. Depending on the printer configuration, the type of print engine support structure may differ. For example, in scanning inkjet printers, one or multiple inkjet printheads may be insertable into a carnage that is moveable bi-directionally over one or multiple carriage bars to define a print zone. In page-wide array printers, multiple inkjet printheads may form a static, or substantially static, print bar that defines a print zone.

Some large format printers are able to print on media up to and over 1 meter in length. Accordingly, the weight of print engine support structures, including the weight of anything supported by the support structure, may be quite considerable. For example, in some printers the print engine support structure may weight in excess of several hundred kilos.

To allow the PPS of such print engine support structures to be accurately adjusted, it is common to provide at least one controllable height adjustor at each end of the print engine support structure. A controllable height adjustor may, for example, comprise a motorized screw mechanism.

To provide optimal print quality, the print engine support structure should be positioned parallel to a printer platen, such that the plane of the printhead nozzle plates is parallel with the printer platen. This ensures that the PPS spacing along the whole length of the platen is constant.

However, where each controllable height adjustor is controllable independently, it may be difficult, or costly, to accurately synchronize the movement of each height adjustor and hence difficult to ensure that the print engine support structure and platen remain parallel. In wide-format printers, the large length of the print engine support structures (which may be in excess of 1 m in length) exacerbates the problem. For example, the large distance between each of end of the print engine support structure makes it largely unfeasible to have utilize mechanically coupled height adjustors.

Referring now toFIG. 1there shown a simplified side view of a printing system100according to one example.FIG. 2shows a corresponding plan view of the printing system100.

The printing system100comprises a print engine support structure102to support one or multiple print engines, such as inkjet printheads104ato104n. As described above, in one example the print engine support structure102may comprise a printhead carriage (not shown) to receive one or multiple inkjet printheads in a scanning inkjet printer configuration. In another example the print engine support structure102may comprise multiple inkjet printheads, or may receive multiple inkjet printheads, in a page-wide array printer configuration.

The printing system100may print on media of different thicknesses, such as a media202shown inFIG. 2, whilst maintaining an optimal PPS height by appropriately adjusting the height of the support structure102above a printer platen106.

The print engine support structure102is positioned above the printer platen106via height adjustors108. In the example shown four height adjustors108ato108dare provided, although in other examples a smaller or greater number of height adjustors may be provided. As shown inFIG. 2, one height adjustor108is provided in the region of each corner of the print engine support structure102. In one example each height adjustor108ato108dis a screw mechanism, although in other examples other suitable mechanisms may be used, such as rack and pinion mechanisms.

Each height adjustor108ato108dis coupled to a respective drive mechanism110ato110d. In one example each drive mechanism is an electric motor, although in other examples other suitable drive mechanisms may be provided, such as hydraulic drive mechanisms or the like.

Each drive mechanism110ato110dis controlled by a print engine support structure controller112, which is shown in more detail inFIG. 3. The controller112comprises a processor302, such as a microprocessor or microcontroller, coupled to a non-transitory computer readable memory304, for example through a communications bus (not shown). The memory304stores print engine support structure control instructions306which are machine readable instructions that, when executed by the processor302, cause the controller112to control the height of the print engine support structure102as described herein in various examples.

The print engine support structure controller112enables the height of the print engine support structure102to be varied by sending appropriate drive signals to each of the drive mechanisms110ato110d. In one example a drive signal may comprise an electrical signal having a predetermined electrical voltage and lasting for a predetermined duration. However, since each drive mechanism may have subtly different characteristics, it is not possible to guarantee that sending the same drive signal to each of the drive mechanisms110ato110dwill result in the same change in height to be achieved by each respective height adjustor. As previously mentioned, however, ensuring uniform PPS height along the length of the support structure102is key to maintaining high print quality.

To ensure uniform PPS height along the length of the support structure102a spatial orientation sensor114is coupled to the support structure102. In one example the spatial orientation sensor114is an accelerometer. In the example shown the accelerometer is shown coupled to an upper surface of the support structure, although in other examples it may be coupled to any appropriate portion of the support structure, either directly or indirectly.

The accelerometer114supplies signals or data that enable the orientation of the accelerometer114to be determined in three-dimensional space. For example, in one example the accelerometer114supplies signals or data that enable its orientation in the x-axis, the y-axis, and the z-axis to be determined. Although shown inFIG. 1as a single device, in one example separate spatial orientation sensors may be used to determine an orientation of each of the x-axis, the y-axis, and the z-axis.

A height sensor116is also provided that provides appropriate signals to the controller112to enable the controller112to determine when a predetermined PPS height has been achieved. The height sensor, may for example, be any electronic device to suitable for measuring distance, and may include, without limitation, a laser, an ultrasound module, a mechanical or optical encoders, or the like.

Each height adjustor108ato108dis associated with a reference position118. In one example the reference position118may be a mechanical reference position, such as the upper surface of the printer platen106. In other examples the mechanical reference position may be provided, for example, by a plurality of mechanical barriers provided at or in proximity to each of the height adjustors108ato108d.

During manufacture of the printer100the height adjustors108are assembled to a high degree of accuracy such that when the support platform102is positioned against the reference position118the support structure102is substantially parallel to the upper surface of the printer platen106, and has hence the same orientation as the printer platen106.

Operation of the printing system100according to one example is described below with reference to the flow diagram ofFIG. 4.

At block402, the controller112obtains reference orientation data from the accelerometer114when the support platform102is in the reference position118. The orientation data defines the orientation of the accelerometer, and hence indirectly defines the orientation of the support platform102, at the reference position.

In one example, the controller112individually controls each of the height adjustors108ato108d, by sending individual drive signals thereto, to move the support structure102to the reference position118to enable the reference orientation data to be determined.

In one example the controller112may determine that the support structure102is against the reference position by sensing an appropriate change in electrical current in each of the drive mechanisms, for example as each drive mechanism experiences an increase in torque as the support structure102is positioned against the reference position118. In other examples the controller112may determine that the support structure102is against the reference position by using a suitable configuration of switches, pressure sensors, or other appropriate sensing devices.

It important to obtain the orientation data whilst the support platform102is in the reference position, since the printer100may be installed such that it is not perfectly level. Accordingly, it is not appropriate to assume that the support platform102is completely level whilst it is in the reference position118.

At block404, the controller112individually controls each of the height adjustors108ato108dto adjust the height of the support structure102to a predetermined height above the printer platen106. The controller112may individually control each of the height adjustors108ato108dto adjust the height of the support structure102until the controller112determines from the height sensor116that the support platform has been adjusted to the predetermined height.

At block406, the controller112obtains orientation data from the accelerometer114to determine the orientation of the support platform at the predetermined height. If the controller112determines that the orientation of the support platform102at the predetermined height matches (within an acceptable degree of tolerance) the reference orientation this indicates that the support platform102is parallel to the platen106and that the PPS height is uniform.

If, however, the controller112determines that the orientation of the support platform102at the predetermined height does not match (within an acceptable degree of tolerance) the reference orientation, the controller112may further control one or more of the height adjustors108ato108dto bring the orientation of the support platform102into the same orientation as the reference orientation. The determination of which height adjustor(s) to adjust may be made based can the determined orientation data.

Once this has been achieved, the controller112may verify, using the height sensor, that the support platform is still at the predetermined height, and if not the controller112may make further control appropriate ones of the height adjustors108ato108dto bring the height of the support platform102to the predetermined height.

The controller112may perform multiple iterations of adjusting the orientation and adjusting the height of the support platform102until the orientation and height are within acceptable tolerances.

In the above-described example the orientation of the support platform102may not be maintained whilst the height of the support platform102is being adjusted. This may occur, for example, if one of the drive mechanisms110ato110doperates at a different speed for a given drive signal.

In some circumstances, however, it may be beneficial, or even critical, to maintain the orientation of the support platform102in its reference orientation whilst it is being raised or lowered. For example, this may help reduce the risk of the support platform102become bent or distorted when the PPS height is adjusted.

Operation of the printing system100according to a further example is described below with reference to the flow diagram ofFIG. 5.

At block502the controller112individually controls each of the height adjustors108ato108dto move the support structure102to the reference position118to enable the reference orientation data to be determined.

At block504, the controller112obtains reference orientation data from the accelerometer114when the support platform102is in the reference position118.

At block506the controller112sends individual drive signals to each height adjustor108ato108dto individually adjust the height of the support structure102. As the height of the support structure102is being adjusted, at block508the controller112obtains orientation data from the support structure102from its current position.

At block510the controller112determines whether any modification to the drive signals being sent to each height adjustor108ato108dshould be made to ensure that the support platform is maintained in the same orientation as the reference orientation whilst the height of the support structure102is being adjusted. If any modifications are deemed appropriate the controller112adjusts the appropriate drive signals being sent.

At block512the controller112determines whether the support platform102has been adjusted to the predetermined height. If not, the above described process continues until the predetermined height is reached and the process stops at block514.

In a further example, shown inFIG. 6, the controller112performs the operations shown in blocks602to610in place of the operation shown in block502ofFIG. 5.

Thus, at block602, the controller112obtains orientation data from the accelerometer114when the support platform102is in its current position.

At block504the controller112sends individual drive signals to each height adjustor108ato108dto individually adjust the height of the support structure102to move the support structure102to the reference position118.

As the height of the support structure102is being adjusted, at block606the controller112obtains orientation data from the support structure102from its current position.

At block605the controller112determines whether any modification to the drive signals being sent to each height adjustor108ato108dshould be made to ensure that the support platform is maintained in the same orientation whilst the height of the support structure102is being adjusted. If any modifications are deemed appropriate the controller112adjusts the appropriate drive signals being sent.

At block610, the controller112determines when the support structure102is in the reference position118. In some circumstances the orientation of the support platform102may have to be adjusted in order to align the support platform102with the reference position118.

The controller112then continues with performing the operations shown in blocks504to514as shown inFIG. 5and as described above.

In this way, the controller112may adjust the height of the support structure102whilst ensuring that the orientation the support structure102remains substantially constant.

It will be appreciated that some examples of the present invention can be realized in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are examples of machine-readable storage that are suitable for storing a program or programs that, when executed, implement examples described herein. Accordingly, some examples provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program.