Displacing a substance

According to some examples a substance displacement apparatus may comprise a gas ejection aperture and a deflector arm. The gas ejection aperture may be to direct gas towards a roller having a surface on which a substance is disposed. The deflector arm may be moveable between a first position in which gas is directed away from a target area on the surface of the roller, and a second position in which gas is directed towards the target area on the surface of the roller, thereby to displace at least some of the substance from the surface of the roller within the target area. A method and a print apparatus are also disclosed.

BACKGROUND

In a printing press, a substance, such as print agent, a coating or a varnish may be applied to a plate mounted on a roller for subsequent transfer onto a printable substrate. In some examples, it may be intended that the substance is not to be transferred onto the substrate from a particular portion of the plate, for example to cause a portion of the substrate corresponding to that particular portion of the plate to remain uncoated or unprinted.

If the position of the portion to remain uncoated or unprinted changes, or the shape of the portion changes, then the plate on the roller may be replaced with a different plate having the new intended printing arrangement. However, producing a new plate and replacing the plate on the roller may be costly and time consuming.

DETAILED DESCRIPTION

Examples in the present disclosure describe apparatus, systems and methods for selectively displacing a substance from a surface, such as a surface of a roller in a printing apparatus, for example.

FIG. 1shows, schematically, an example of a printing system100in which it may be intended to displace substance from a surface of a roller. The printing system100may include a first roller102, such as an anilox roller. An anilox roller may, in some examples, comprise a metallic core surrounded by a ceramic coating. The surface of the ceramic coating may include thousands or millions of indentations, referred to as cells, having a defined capacity. A substance, such as print agent, primer, ink, varnish or the like, may be deposited on the roller, for example from a substance container or source104. Excess substance may be removed (e.g. scraped) from the surface of the roller using a doctor blade106and/or a substance displacement apparatus200(discussed in greater detail below). A defined amount of the substance may be left in the cells. The first roller102may then be rotated in contact with a printable substrate108, which may be in the form of individual sheets or a web (as shown in the example ofFIG. 1). In some examples, the system100may further include a second roller110, such as a nip roller, which rotates in an opposite direction to the first roller102, and which serves to urge the printable substrate108towards the first roller while print agent is transferred from the first roller onto the printable substrate. In some examples, the second roller110may be omitted or replaced with some other component, such as a support to support the printable substrate108.

During some printing jobs, it may be intended to prevent any substance from being deposited onto a particular area or region of the printable substrate108, or at least restrict the amount of substance deposited onto the particular area or region. For example, when printing a web or net to be formed into a packaging container, such as a carton for food or drink, it may be intended that some parts of the carton (e.g. attachment tabs) are to be glued and stuck to other parts of the packaging web and, therefore, should not receive any print agent. In other examples, such a packaging web may be coated in a waterproof coating or varnish. Again, it may be intended that some portions of the packaging, such as the tabs, are not to be coated by the varnish or coating. In another example, it may be intended that a region on the packaging web is to remain unprinted (referred to as a knockout), so that a “use by” or “best before” date may be printed subsequently in that region. In such examples, in order to prevent substance (e.g. ink or varnish) from being deposited onto the printable substrate108, the print agent may be removed or displaced from those cells on the anilox roller102which correspond to the region to remain unprinted or uncoated. As discussed in detail below, the substance displacement apparatus200serves to selectively remove or displace a substance from a region or regions on the roller102.

While the example system100discussed above includes an anilox roller102, in other examples, rollers of other types may be included in the system instead of, or in addition to, the anilox roller. For example, the substance displacement apparatus200may remove print agent from the surface of a roller other than an anilox roller, which is intended to be used to transfer print agent (or some other substance) onto a printable substrate108.

In general, the substance displacement apparatus200uses a flow of gas to displace a substance, such as print agent or varnish or the like, from a surface of a roller. Various gases or combinations of gases may be used, such as compressed air, carbon dioxide, nitrogen, or the like. In some examples, high humidity compressed air may be used as this may reduce the drying effect of water-based substances. In order to achieve accurate control over the flow of the gas and, therefore, over the regions on the roller at which the gas is directed, the substance displacement apparatus200uses a mechanism for deflecting the flow of gas into an intended direction.

FIG. 2is a simplified schematic of an example of the substance displacement apparatus200. The substance displacement apparatus200comprises a gas outlet, or gas ejection aperture202, to direct gas towards a roller having a surface on which a substance is disposed; and a deflector arm moveable between a first position in which gas is directed away from a target area on the surface of the roller, and a second position in which gas is directed towards the target area on the surface of the roller, thereby to displace at least some of the substance from the surface of the roller within the target area. In some examples, the roller may comprise a roller such as the anilox roller102. Thus, in general, when it is intended to direct gas towards the surface of the roller so as to displace the substance from the roller surface in a particular area, the deflector arm may be positioned such that the flow of gas is towards the particular area on the roller surface. However, when it is not intended for the flow of gas to be directed towards the particular area on the roller (e.g. when it is intended for the substance to remain on the surface of the roller in that particular area), then the deflector arm may be positioned such that the gas flow is not towards the particular area on the roller surface, or is prevented from reaching the particular area of the roller surface.

FIG. 3shows, schematically, a cross-section through one particular example of the substance displacement apparatus200. In the example shown inFIG. 3, the gas ejection aperture202is located between a first housing portion302and a second housing portion304. The deflector arm204extends into the gas ejection aperture202between the first and second housing portions302,304. In some examples, the deflector arm204may at least partially through the gas ejection aperture202between the first and second housing portions302,304.

In some examples, the substance displacement apparatus200may also include a chamber either side of the deflector arm204, each chamber to hold gas prior to ejection by the gas ejection chamber202. In the example shown inFIG. 3, the substance displacement apparatus200includes a first chamber306and a second chamber308. The chambers306,308may be of any shape. In the example shown inFIG. 3, the chambers306,308are defined by internal side walls302a,304aof the first and second housing portions302,304respectively, the deflector arm204and front and back walls (not shown) of the first and second housing portions. In some examples, gas may be received in the first and second chambers306,308through respective gas inlets310,312. In this example, the gas inlets310,312are in communication with the first and second chambers306,308respectively via conduits314,316. The conduits may be formed through the first and second housing portions302,304. Gas may travel from the chambers306,308, through the gas ejection aperture202, towards the roller102. However, as is clear from the discussion below, in some examples, the deflector arm204may restrict or prevent the flow of gas from one of the first and second chambers306,308, depending on its position.

The substance displacement apparatus200may, in some examples, also comprise a gas guide element318and/or a substance guide element320. Details and functionality of the gas guide element318and the substance guide element320are discussed below.

FIG. 4is a simplified schematic of an example of the substance displacement apparatus200. In the example shown inFIG. 4, the substance displacement apparatus200includes the gas ejection aperture202and the deflector arm204. The apparatus200may further comprise the gas guide element318. The gas guide element318may be positioned relative to the gas ejection aperture202to guide gas which is directed away from the target area away from the roller. In some examples, the apparatus200may further comprise the substance guide element320. The substance guide element320may be positioned relative to the gas ejection aperture202to guide gas which is directed towards the target area, and the substance removed from the target area, away from the roller. In some examples, the substance displacement apparatus200may further comprise the first chamber306and the second chamber308. The chambers306,308may be either side of the deflector arm204, each chamber to hold gas prior to ejection via the gas ejection aperture202.

FIGS. 5 and 6are simplified schematics of a portion of the substance displacement apparatus200shown inFIG. 3, with the deflector arm204in the first position and the second position respectively. InFIG. 5, the deflector arm204is shown in the first position which, in this example, is to the left-hand side of the gas ejection aperture202. In other examples, the positions may be reversed, such that, in the first position, the deflector arm204is to the right-hand side of the gas ejection aperture202. Thus, the deflector arm204may touch the first housing member302at the location of the gas ejection aperture202, and may be spaced apart from the second housing member304. In this way, while the deflector arm204is in the first position, gas from the first chamber306may be prevented from exiting the first chamber through the gas ejection aperture202, while gas from the second chamber308may be able to exit the second chamber through the gas ejection aperture, as indicated by arrow A.

InFIG. 5, the roller102is shown located below the substance displacement apparatus200. However, in other examples, the roller102and the apparatus200may be arranged in any orientation about one another. For example, the apparatus200may be positioned below the roller102, as shown in the example arrangement ofFIG. 1. It will be apparent that, since the roller102rotates with respect to the apparatus200in use, the target area on the roller surface will also move relative to the apparatus. Therefore, in order to displace a substance from the surface of the roller102within a target area504, gas may be ejected through the gas ejection aperture202towards the roller for a duration that it takes for the whole target area to pass under the part of the gas ejection aperture through which gas is ejected.

The gas ejection aperture202may be positioned such that gas flowing from the first and/or second chambers306,308is directed at least initially to towards the roller102. In the example ofFIG. 5, gas that is able to flow from the second chamber308through the gap formed between the deflector arm204and the second housing member304is directed onto the gas guide element318. In some examples, the gas guide element318may comprise a lip502to prevent gas which is directed away from the target area from flowing towards the target area after ejection. In other words, the lip502may prevent the flow of gas (or at least most of the gas flow) ejected from the second chamber308from reaching the target area. The lip502deflects any gas ejected from the second chamber308away from the target area, generally in the direction indicated by arrow B. In some examples, the gas guide element318guides the flow of gas along an outer surface of the second housing member304. The gas may, in some examples, then be recycled, or ejected into the atmosphere.

In other examples, the gas guide element318may not include a lip, but the gas may be directed away from the target area504in some other way. In some examples, a shape or configuration of the substance displacement apparatus200may cause gas to be directed away from the target area504. For example, the gap formed between the deflector arm204and the second housing member304may be defined by portions of the apparatus200that are shaped and/or angled such that the gas is directed away from the target area. In some examples, a suction mechanism, or vacuum forming mechanism may be used to suck ejected gas away from the apparatus, and/or the roller102. Such a suction mechanism may form part of the apparatus200, or may be associated therewith.

InFIG. 6, the deflector arm204is shown in the second position which, in this example, is to the right-hand side of the gas ejection aperture202. In this position, the deflector arm204is touching the second housing member304at the location of the gas ejection aperture202, and is spaced apart from the first housing member302. In this way, while the deflector arm204is in the second position, gas from the second chamber308is prevented from exiting the second chamber through the gas ejection aperture202, while gas from the first chamber306is able to exit the first chamber through the gas ejection aperture, as indicated by arrow C.

In this example, gas flowing through the gap formed between the deflector arm204and the first housing member302is directed onto the surface of the roller102. Thus, when the deflector arm204is in the second position, gas may be ejected from the first chamber306, towards the target area504of the roller102, so as to displace a substance from the target area of the roller. Gas ejected from the apparatus200may flow at a rate depending on the intended use (e.g. the nature and amount of substance intended to be displaced). In some examples, the rate of flow of gas from the apparatus200may depend on the pressure of gas in the first and second chambers306,308. The rate of flow of gas from the apparatus200may be variable. In some examples, the rate of flow of gas from the apparatus200may be sufficient to displace the substance from the roller102.

As noted above, gas ejected from the apparatus200while the deflector arm204is in the second position (as shown inFIG. 6) is directed at least initially towards the target area504of roller102. The ejected the gas and/or substance which has been displaced from the surface of the roller102(and from any cells present in the surface of the roller) may be directed away from the roller by the substance guide element320. The substance guide element320may, in some examples, direct substance and/or gas away from the roller102along a path formed between the substance guide element and an outer surface of the first housing member302, generally in the direction indicated by arrow D. In the example shown inFIG. 6, the lip502of the gas guide element318may prevent the flow of gas and/or substance ejected from the first chamber306from flowing into the channel formed by the gas guide element318and the second housing member304. In this way, the lip502may serve as a barrier to help to deflect substance and/or gas in the direction of the arrow D. Again, in some examples, a suction mechanism, or vacuum forming mechanism may be used to suck ejected gas away from the apparatus, and/or the roller102. Such a suction mechanism may form part of the apparatus200, or may be associated therewith.

In some examples, a thickness t of the deflector arm204may be fractionally smaller than a width of the gas ejection aperture202. In this way, wherein the deflector arm204is in contact with one of the first or second housing members302,304, the gap formed between the deflector arm and the opposing housing member is relatively small, but large enough to allow the gas to flow therethrough. In some examples, the deflector arm204may extend at least partially through the gas ejection aperture202. A gap through which the gas is directed may, in some examples, have a width of less than approximately 100 micrometres. In some examples, the gap may have a width of between approximately 50 micrometres and 100 micrometres. In other examples, the gap through which the gas is directed may have a larger width. However, a smaller width may cause the gas to be ejected at a greater rate, thereby improving the substance displacement.

In use, the deflector arm204may be moved between the first position (shown inFIG. 5) and the second position (shown inFIG. 6) to cause gas to flow onto the surface of the roller102in the target area504, as intended. For example, when it is intended that any substance on the surface of the roller102is to remain (i.e. not be displaced), and therefore be transferred onto the printable substrate108, then the deflector arm204may be moved into the first position. In this way, gas from the second chamber308may be caused to exit the second chamber through the gap formed between the deflector arm204and the second housing member304, and deflected away from the roller102, without any substance being displaced from the roller surface. If it is intended that a particular portion of the printable substrate108is to remain unprinted or uncoated, then the deflector arm204may be moved into the second position. In this position, gas from the first chamber306is caused to exit the first chamber through the gap formed between the deflector arm204and the first housing member302, towards the target area504of the roller102. As the roller102rotates, the gas is directed towards the roller surface, thereby causing any substance on the surface to be displaced in the direction of the arrow D. In this way, when the target area504of the roller102comes into contact with the printable substrate108, no substance will be transferred onto the printable substrate from the target area. Once the roller102has rotated through the extent of the target area504, the deflector arm204may be moved into the first position, so as to prevent any further substance from being displaced from the roller surface.

The deflector arm204may be moved between the first position in the second position in a number of ways. In some examples, the deflector arm may be formed from a piezoelectric material. A piezoelectric material is a material that exhibits the piezoelectric effect (or the reverse piezoelectric effect), whereby a mechanical strain is generated in the material in response to the application of an electric field (e.g. a voltage) through the material. Thus, in some examples, the deflector arm204may be formed from such a piezoelectric material, such that, when no electric field is applied through the deflector arm, the deflector arm is in the first position and, when an electric field is applied through the deflector arm, a mechanical strain is generated, causing the deflector arm to move into the second position. When the electric field is removed, the deflector arm204may be caused to move back into the first position.

In some examples, the deflector arm204may be substantially planar in shape. In other words, the deflector arm may have a sheet-like configuration. The width of the deflector arm may, in some examples, depend on the intended resolution at which the substance displacement apparatus200is to displace substance from the roller102. For example, the smallest area on the surface of a roller that could be displaced by a deflector arm204having a width of 1 cm would have a width of 1 cm (and a length determined by the duration that the deflector arm remains in the second position). However, by forming the deflector arm204such that it has a smaller width, an area on the surface of the roller from which substances to be displaced may be smaller. In some examples, the intended resolution may be less than approximately 2 mm. For example, the resolution may, in some examples, be approximately 1 mm or 0.5 mm. Thus, in such examples, the width of each deflector arm204may be 2 mm, 1 mm or 0.5 mm. In other examples, the deflector arm may have a larger width.

In some examples, multiple deflector arms204may be arranged adjacent to one another (e.g. side-by-side). This may increase the width of the area on the surface of the roller102from which substance may be displaced. In some examples, the substance displacement apparatus200may include multiple deflector arms204, each having a relatively small width, such that the precise area or areas on the surface of the roller in which substances to be displaced may be accurately selected and/or controlled. An example of the use of multiple deflector arms204is shown in the example ofFIG. 3. In that example, the deflector arm204may be considered to be a deflector arm array, formed of multiple individual deflector arms arranged side by side. Such a deflector arm array is shown more clearly inFIG. 7.

FIG. 7is an exploded perspective view of an example of the substance displacement apparatus200. In this example, the first housing member302is shown in its normal position relative to the deflector arm204, while the second housing member304shown in an exploded manner, separated from the deflector arm. According to this example, the deflector arm204may include an electrical contact portion702and a plurality of deflector arm elements2041to204N. The electrical contact portion702of the deflector arm204may receive an electrical current corresponding to one of the deflector arm elements. In some examples, the electrical contact portion702of the deflector arm204may receive an electrical current corresponding to multiple deflector arm elements. In some examples, the electrical contact portion702may comprise multiple electrical contact portions. For example, the electrical contact portion702may comprise an individual electrical contact portion for each deflector arm element2041to204N. In this way, the movement of each deflector arm element between the first position in second position may be independently controlled.

The present disclosure also relates to method for displacing a substance.FIG. 8is a flowchart of an example of a substance displacement method800. The method800comprises, at block802, directing gas from a gas outlet202towards a surface of a roller102, the surface having a substance disposed thereon. At block804, the method800comprises selectively moving a deflector arm204between a first deflection configuration in which gas is directed away from a defined region on the surface of the roller, and a second deflection configuration in which gas is directed towards the defined region on the surface of the roller, thereby to displace some or all of the substance from the surface of the roller within the defined region. The method800may, in some examples, be performed by, or using, the substance displacement apparatus200discussed above.

By displacing a substance from the surface of a roller using the methods disclosed herein, the positioning of the substance on a printable substrate can be accurately controlled and selected. The disclosed methods provide a digital alternative to previous methods, in which a plate mounted on the surface of the roller would be replaced when the removal of substance from a particular area was intended.

FIG. 9is a flowchart of a further example of a substance displacement method900. The method900may comprise, at block902, directing gas into a first chamber306located at a first side of the deflector arm and a second chamber308located at a second side of the deflector arm204, the first and second chambers to store the gas prior to being directed from the gas outlet202.

In some examples, gas is directed into the first and second chambers306,308so as to maintain a gas pressure in the first chamber306which is approximately equal to a gas pressure in the second chamber308. In some examples, the approximately equal pressures in the first and second chambers306,308may be achieved by maintaining a flow of gas into the first chamber when the deflector arm204is in such a position or configuration that gas is able to exit the first chamber via the gas outlet202, and by maintaining a flow of gas into the second chamber when the deflector arm is in such a position or configuration that gas is able to exit the second chamber via the gas outlet. In other words, while the substance displacement apparatus200is in use, a constant flow of gas may be provided to the first chamber306and/or the second chamber308. By maintaining an approximately equal, stable pressure in the first and second chambers306,308, the deflector arm204is not caused to move (e.g. between the first and second deflection configurations) as a result of a difference in pressure. Furthermore, with approximately equal gas pressure in both the first and second chambers306,308, the deflector arm204may be moved between the first and second deflection configurations with the application of a relatively low force. Thus, when the deflector arm204is formed from a piezoelectric material, movement between the first and second deflection configurations may be achieved using a relatively small power.

In some examples, the pressure of gas in the first chamber306and/or second chamber308may be approximately 5 bar. In some examples, the pressure in the chambers may be higher or lower than approximately 5 bar.

As noted above, the deflector arm204may, in some examples, comprise a piezoelectric material. In such examples, the method800,900, may further comprise applying a voltage to the piezoelectric material to cause the deflector arm204to move between the first deflection configuration and the second deflection configuration.

The present disclosure also relates to a print apparatus. The print apparatus may, for example, comprise the substance displacement apparatus200disclosed herein.FIG. 10is a simplified schematic of an example of a print apparatus1000. The print apparatus1000comprises a roller1002having a surface on which to receive a substance to be transferred to a printable medium. The print apparatus1000also comprises a gas delivery unit1004for directing gas towards the roller. The gas delivery unit1004may comprise a gas outlet1006; and a gas deflector1008moveable between a first position in which gas is directed from the gas outlet away from a target area on the roller surface, and a second position in which gas is directed from the gas outlet towards the target area on the roller surface, thereby to displace at least some of the substance from the target area of the roller surface. The gas delivery unit1004may, in some examples, comprise, or be similar to, the substance displacement apparatus200.

The print apparatus1000may comprise any type of print apparatus which includes a roller for receiving a substance, such as print agent, primer, ink, varnish, or the like. In some examples, the roller may comprise an anilox roller, for use in a flexographic print apparatus.

As noted above, the substance displacement apparatus200, for the gas delivery unit1004, may, in some examples, be combined with other similar units.FIG. 11is a simplified schematic of a further example of a print apparatus1100which includes multiple gas delivery units. The print apparatus1100includes the roller1002, and may further comprise a plurality of gas delivery units1004ato1004f, each having a gas outlet and a gas deflector, the plurality of gas delivery units arranged linearly over a length of the roller. In the example shown inFIG. 11, the print apparatus1100includes six gas delivery units1004ato1004f. However, in other examples, the print apparatus1100may include more or fewer gas delivery units. As will be apparent from the discussion above, each gas delivery unit may include multiple gas deflectors. For example, each gas delivery unit may include70gas deflectors, each gas deflector having a width of 1 mm. A print apparatus may, in some examples, include10gas delivery units. Therefore, such a print apparatus may include700gas deflectors with a resolution of 1 mm. Each gas deflector may be individually controllable such that the precise area of the roller from which a substance is to be displaced can be accurately controlled. Thus, in some examples, the gas deflector204of each gas delivery unit1004may be movable independently of the gas deflector of each other gas delivery unit.

The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart.

While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above-mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims. Features described in relation to one example may be combined with features of another example.