Patent Publication Number: US-11377316-B2

Title: Media conveyors with suction holes

Description:
BACKGROUND 
     In some media handling apparatus, such a printers, media stackers or the like, media conveyors, such as belt-type conveyors, rollers or pallets on an endless track are used to convey media, for example media on to which text or an image may be printed. For example, such media conveyors may be used to convey media from a media storage area to a position in which it can be printed (for example, near a printhead of the printer or the like) and then to convey the media to a curing and/or collection area. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Non-limiting examples will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of an example media conveyor; 
         FIGS. 2A and 2B  show an example diaphragm of a valve; 
         FIGS. 3A and 3B  show an example valve in situ in a print media transport apparatus; 
         FIG. 4  is a schematic diagram of another example media conveyor; 
         FIGS. 5 and 6  are schematic diagrams of example media handling apparatus; and 
         FIG. 7  is a flowchart of an example method of conveying a media sheet. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic diagram of an example of a media conveyor  100  comprising a media support platform  102 . A suction hole  104  is provided through the media support platform  102  (which may be a moving platform, or may be covered with a belt or the like), and a valve  106  is arranged to selectively close the suction hole  104 . Associated with the valve  106  is a valve actuator  108  comprising an air tube  110  having an air inlet  112  (in this example, the end of the tube  110 , although this could be positioned elsewhere on the tube  110 ) and a seal  114 , which is to selectively seal the air inlet  112 . In some examples, the valve  106  may be a pressure operated valve, for example being actuated to selectively close or open the suction hole  104  by a pressure differential in or around the valve  106 , wherein the pressure differential may be controlled by sealing or un-sealing the inlet  112  of the air tube  110 . 
     Media conveyors may for example be used in a print apparatus or some other apparatus. In such apparatus, a media conveyor may be used in order to move media, for example a sheet material, such as paper, card stock, plastics, and the like, which may be rigid, substantially rigid or flexible. 
     Suction may be used to secure the media to a conveyor, for example by drawing air through suction hole(s) in the platform. In previous examples of media conveyors, such suction hole(s) are always open. However, this can result in wasted energy and/or the specification of large vacuum sources, which can be expensive. For example when a media sheet which is narrower than the support platform  102  on which it is transported, in order to maintain suction on the media while air is drawn through uncovered holes, additional power is consumed. In some examples, or in some media handling phases, the air is heated (for example to aid drying or curing of a printed media), and drawing air though open holes effectively wastes the energy consumed in heating the air, and/or may make it difficult to reach a target temperature for the process being carried out. 
     In some previous examples of media conveyors, holes may be selectively closed using, for example, electrically actuated valves. However, such valves can be expensive and may operate in a relatively hostile environment, which may be hot (for example, up to 90° C.), and apparatus, such as print apparatus, can contain condensation of water and solvents which can be damaging to valve apparatus. Some working practices include manually taping over holes when printing a particular media so as to selectively close suction holes, but this is burdensome on a user. In still further examples, holes may be generally sealed but opened by the presence of a media. For example, a media sheet may cover a pilot hole, which may be smaller than a suction hole, and this may create a pressure differential which opens a valve (for example, moves a moveable diaphragm) covering a suction hole. However, this relies on the media sheet successfully sealing a suction hole. In some examples, this cannot be assured. For example, as is described in greater detail below, a fabric or otherwise porous belt may be provided on the platform  102  and this could impede a seal from forming. 
     In some examples, the media conveyor  100  may comprise a negative pressure source, for example as described below. 
     An example of a diaphragm  200 , which could provide a component of a valve  106 , is shown in different views in  FIGS. 2A and 2B . In this example, the diaphragm  200  comprises a resilient (for example, rubber, plastic or the like) diaphragm having a convolution comprising a pair of concentric annular walls  202   a ,  202   b , which in this example are substantially parallel and are joined at a base region thereof by a flexible portion  206 . The diaphragm  200  also comprises a sealing surface  204  and a seat  208 , which may interface with other apparatus portions as shown in  FIGS. 3A and 3B  below. 
       FIGS. 3A and 3B  show examples in which a valve  301  comprising a diaphragm  200  is in situ under a media support platform  300 . 
     In this example, the media support platform  300  comprises a plurality of perforations  302  in communication with a suction hole  104 , although in other examples a suction hole  104  may be formed through to the surface of the platform  300 . The seal  114  is mounted on a piston  304  which is connected to a drive mechanism, in this example a solenoid  306 , such that the position thereof relative to the end of the air tube  110  (which is shown in a broken fashion to indicate that the tube  110  may be longer than illustrated) may be adjusted to block and unblock the inlet  112  at the end of the air tube  110 . The solenoid  306  may act against a resilient member, in the example of the Figures, a spring  308 . In this example, the positions of the seal  114  are bi-stable: the spring  308  will urge the seal  114  to seal the end of the air tube  110  or the solenoid  306  will draw the piston into a retracted, latched, position. 
     A solenoid is an example of a robust, low cost drive mechanism which is readily controlled with a simple control system such as an electric pulse. In other examples, other drive mechanisms could be used, for example stepper motors, servos, manual actuation, or the like. 
     By providing a drive mechanism which is bi-stable, energy is consumed just at the point of state change and therefore power consumption and risk of component burn-out is reduced. 
     The air tube  110  is connected to a chamber  310  on a first side of diaphragm  200  within the valve  301  and the valve  301  further comprises a region  312  on the second side of the diaphragm  200  within the valve  301 . The chamber  310  and the region  312  are in fluid communication with a vacuum source. The chamber  310  is in fluid communication with a vacuum source via a bleed hole  314 , which is smaller than the aperture of the air tube  110  (for example, half or a quarter of the surface area). The region  312  on the second side of the diaphragm  200  is arranged so as to have a relatively unrestricted air flow with the vacuum source (when compared to the restriction presented by the bleed hole  314 ). 
     In both  FIGS. 3A and 3B , a vacuum is applied, as shown in  FIG. 3B . In some examples, vacuum pressures may range between a few hundred to a few thousand Pascals, resulting in a suction force of around 500 Pa to 1000 Pa. 
     In  FIG. 3A , the solenoid  306  acts to retract the seal  114  and unseal the end of the air tube  110 . The chamber  310  on the first side of the diaphragm is at or slightly below atmospheric pressure: air enters the chamber  310  via the air tube faster than it is removed by the vacuum source via the bleed hole  314  due to their relative sizes. However, the applied vacuum reduces the pressure within the region  312  on the second side of the diaphragm and the resulting pressure difference deforms the diaphragm  200  from its equilibrium shape shown in  FIG. 2 , and causing it to seal the mouth of the suction hole  104 . As the suction hole  104  is closed there is no airflow though the perforations  302  and any media on top of the perforations  302  would not be subject to a suction force. 
     In  FIG. 3B , the latch holding back the seal  114  has been released allowing the spring  308  to act on the seal  114  to urge it toward the end of the air tube  110 . The vacuum acts to draw air through the bleed hole  314  and, as this is no longer replaced via the air tube  110 , the pressure in the chamber  310  under the sealing surface  204  reduces, causing the sealing surface  204  to be drawn downwards until the diaphragm  200  assumes its rest position and, the sealing surface is a distance H from the mouth of the suction hole  104 . As a result, the vacuum acts such that air is drawn through the perforations  302  and the suction hole  104 . A sheet of media on the platform  300  will therefore be held by a suction force. 
     As mentioned above, the cross sectional surface area of the bleed hole  314  is less than that of the air tube  110 . In some examples, the diameter of the bleed hole  314  may be in the order of a few millimeters, for example, 1 to 3 mm, whereas the diameter of the air tube  110  may be around 16-20 mm. More generally, the ratio between these sizes (or the size of the inlet  112 , if different from the size of the tube  110 ) will determine the response time of the diaphragm  200 . In some examples, the diameter of the bleed  314  hole is significantly less than the diameter of the air tube  110 . 
     The drive mechanism of the seal  114  (in this example, the solenoid  306 ) may be some distance from the diaphragm  200 , for example being located somewhere other under the platform  300 . This may reduce the burden for maintenance and replacement of such components, which may be provided in a relatively more accessible location. In some examples, the seal  114  and the associated actuation mechanism may be arranged outside a relatively hostile environment which may be created under the platform  300 . 
       FIG. 4  shows a schematic example in which a plurality of valves  106   a ,  106   b , in this example a first  106   a  and a second  106   a  valve, associated respectively with a first  104   a  and second  104   b  suction hole, are in fluid communication such that the valve actuator  108  can actuate both (or more generally, any number) of the valves as a group using a single seal  114 . Each of these valves may comprise a valve  106  which is responsive to a pressure differential, for example comprising a valve  301  as shown in  FIG. 3A or 3B . If the valves were as shown in  FIGS. 3A and 3B , the chambers  310  under the diaphragms  200  of a plurality of valves  301  may be connected, for example by an air tube such as the air tube  110  described above, or in some other way. The regions  312  on the second side of the diaphragms  200  may be in fluid communication (for example, comprising part of the same negative pressure chamber, for example being connected to the same vacuum source(s), or could be separate from one another. 
     In this way, ‘sectorisation’ of the suction provided under a platform  102  may be provided. For example, the valves may be controlled as columns, which may run the whole or part of the length of the platform  102 . As media can vary in width, this allows the width over which suction is provided to be tailored to a particular media being conveyed. In other examples, the platform may be divided into zones, with the media being passed from one zone to the next. Suction may be provided (i.e. valves controlled such that the suction holes are opened) to coincide with the presence of media in a zone. 
     The complexity of control of individual valves or a large number of groups of valves may be balanced with the versatility of the apparatus for a particular intended use. For example, smaller groups of valves  106  controlled by a single actuator  108  (or providing more valves which may be controlled individually) allow a region of the platform  102  which provides suction to closely match the size of the particular media being processed. This in turn allows for energy efficiency and allows, for example, lower power vacuum sources to be used to provide a threshold suction. However, the control system of such a versatile arrangement may be more complex that an arrangement in which fewer, larger groups of valves  106  are controlled by a single valve actuator  108 . 
     The maximum number or configuration of valves  106  controlled in a group depends on the airflow losses in the air tube  110 , and the ratio between the tube diameter and the bleed hole size. In some examples, around two to ten valves  106  may be controlled in a group, although a group could comprise more than ten valves  106 . 
       FIG. 5  is an example of a media handling apparatus  500  comprising a media support platform  502 , a valve actuator  504 , a negative pressure source  506  and processing circuitry  508 . 
     The media support platform  502  comprises a plurality of suction holes  510   a - g  (generally referred to with reference numeral  510 ). In association with a first suction hole  510   a  of said suction holes  510 , there is a first valve  512   a  to selectively close the associated suction hole  510   a . In this example, the first valve  512   a  comprises a diaphragm having a position which is responsive to a pressure differential, which may for example comprise a diaphragm  200  as described in relation to  FIGS. 2 and 3  above. 
     The valve actuator  504  in this example comprises an air tube comprising a selectively sealable inlet (for example as shown in relation to  FIGS. 1, 3 and 4 ) and may selectively actuate the first valve  512   a.    
     The negative pressure source  506  is arranged, in use of the apparatus  500 , to cause suction of air through a suction hole  510  when that suction hole  510  is open. The negative pressure source  506  in this example comprises an axial fan, but other vacuum sources such as vacuum pumps, centrifugal blowers, other types of fans or the like may be used. 
     The processing circuitry  508  is arranged to determine, based on an attribute of a media being handled by the media handling apparatus  500  (for example, conveyed, printed or the like), if the first suction hole  510   a  should be open or closed and to control the valve actuator  504  according to the determination. For example, the attribute may comprise at least one dimension, such as a length or width, another physical characteristic such as weight, thickness, porosity (permeability) or stiffness, or the position of the media within the apparatus  500 . In some examples, such attributes may be provided for example by a user of the media handling apparatus  500 . Combinations of attributes may be considered. In some examples, the media handling apparatus  500  may comprise detectors to detect at least one attribute of the media. For example, edge detectors may be provided to detect the edge positioning, media detectors may detect the presence of media, thickness detectors may detect a substrate thickness and the like. 
     In this example, the drive mechanism of the valve actuator  504  is provided remotely from the platform  502 . This may be, for example, in a region of the apparatus  500  which is away from vacuum and/or high temperature conditions, free from vapours and condensation and/or more readily accessible for maintenance purposes. 
       FIG. 6  is another example of a media handling apparatus, in this example a print apparatus  600  comprising a media support platform  502  and processing circuitry  508 . A media conveying belt  602  is provided to carry media across the media support platform  502 . This may for example be a fabric, plastic mesh or otherwise permeable endless belt (in some examples, driven with at least one roller (not shown). However, in other examples, the platform  502  may comprise, for example, a loop of pallets. 
     In this example, the print apparatus comprises a first  504   a  and second  504   b  valve actuator as well as a first  506   a , second  506   b  and third  506   c  negative pressure source. Each negative pressure source  506   a - c  is associated with a respective negative pressure chamber  604   a - c . The negative pressure chambers  604   a - c  are at least substantially separate from one another, and each is associated with a different subset of suction holes  510 . In this way, each negative pressure source  506   a - c  may draw air through a different subset of the suction holes  510  (wherein a subset comprises at least one suction hole  510 ). 
     In this example, the negative pressure sources  506   a - c  are shown to be within the belt  602 , although this may not be the case, and at least one duct may be provided between each source  506  and a negative pressure chamber  604 . 
     The presence of such a belt  602  assists in smoothly conveying the media, but may interfere with a seal being formed simply by the presence of media on the belt, as air can leak through the belt  602  itself into a pilot hole or the like, even when the media overlies such a hole. 
     Providing a plurality of negative pressure sources  506   a - c  means that a source  506   a - c  may be selected according to the region with which it is associated. For example, it may be that different regions are associated with different stages of media handling, for example operating at different temperatures and/or preforming different functions, which may in turn mean that different suction levels are intended. In such examples, providing a plurality of sources  506   a - c  may allow a source  506  to be selected which is compatible with its intended operation. It may also allow smaller or less powerful negative pressure sources  506  to be employed, which may be less expensive and more readily available than a single, more powerful negative pressure source  506 . Providing a plurality of negative pressure chambers  604   a - c  may also facilitate the provision of different negative pressure conditions in different regions. In some examples, the negative pressure chambers  604   a - c  may include the regions  312  on the second side of the diaphragms  200  described in relation to  FIGS. 3A and 3B  above. 
     In the example of  FIG. 6 , a first  512   a  and second  512   b  valve are selectively to close a first  510   a  and second  510   b  suction hole under control of the first valve actuator  504   a . A third  512   c , fourth  512   d  and fifth  512   e  valve are selectively to close a third  510   c , fourth  510   d  and fifth  510   e  suction hole under control of the second valve actuator  504   b . A sixth suction hole  510   f  is closed by a valve  512   f  directly actuated by presence of media. For example, the media may pass over the top of a pilot hole which acts in the same way as sealing the end of the air tube  110 . A seventh suction hole  510   g  is not associated with a valve and is always open. This may allow for pressure release and/or may for example be a suction hole  510  in the centre of the platform which is more likely to carry media, if when the media is narrow. More generally, a print apparatus or a media conveyor or a region thereof may comprise a combination of valves having different (or in some examples, no) actuation mechanisms. 
     As noted above, in this example, each of the negative pressure sources  506   a - c  is associated with a different negative pressure chamber  604   a - c  which in turn is connected to cause suction of air through a subset of the suction holes  510 . At least one, and in some examples, each, negative pressure chamber  604  may comprise a sensor to monitor the pressure level. Such a sensor may provide feedback to a negative pressure source  506 . 
     In this example, a first negative pressure chamber  604   a  is associated with a region of the media support platform  502  which is to support a print media during a first print operation (for example, drying and curing), the second negative pressure chamber  604   b  is associated with a region of the media support platform  502  which is to support a print media during a second, different print operation (for example, printing inks, toners and the like onto media by means of a printhead mounted on a moveable carriage, or an array of static print heads or the like, which may eject drops of ink through orifices or nozzles and towards a print media so as to print onto the media), and the third negative pressure chamber  604   c  is associated with a region of the media support platform  502  which is to support a print media during a second, different print operation (for example, loading the print media into the print apparatus  600 ). 
     In some examples, different regions of the media support platform  502  comprise different compositions of suction holes. For example, it may be that, in a printing region, it is to be assured that more suction is applied than in a loading region as in such a section print apparatus components such as print heads may pass close to the media and therefore holding the print media securely may reduce smearing or misapplication of the print agent. This could be achieved by provided more actuatable valves  512  in the printing region than in the loading region, such that suction is not wasted due to un-sealed suction holes  510 . In a drying or curing region, hot air may be provided and in order to prevent wasting energy, it may be of relatively higher concern to seal off otherwise uncovered suction holes  510  in such a region than in other regions. Therefore, it may the case that valves are controllable to a higher resolution in such a region (i.e. smaller groups of valves  512  are controlled by a single actuator). In some examples, the configuration may be a configuration of groups of valves controlled by a single valve actuator  504 . For example, in one region, the resolution of the groups may be different than in another, or the groups may comprises different shapes or forms. In some examples, varying the composition of suction holes may comprises varying the provision of holes which are always open and/or holes which are associated with valves which are controlled in some other way than by sealing an air tube. 
       FIG. 7  is a flow chart of an example of a method comprising, in block  702 , receiving, on a media support platform of a media handling apparatus, a media sheet. Block  704  comprises generating a negative pressure. In block  706 , an actuation signal is generated to selectively seal an inlet to an air tube and thereby cause a pressure operated valve to communicate the negative pressure to the media sheet as an applied suction. In some examples, sealing the air tube causes a plurality of pressure operated valves to communicate the negative pressure to the media sheet as a suction via a plurality of respective suction holes. Block  708  comprises conveying the media sheet on the media support platform under the applied suction. The method may be a method of operating the media handling apparatus  500  or the print apparatus  600   
     Examples in the present disclosure can be provided as methods, systems or machine readable instructions, such as any combination of software, hardware, firmware or the like, which may for example be executed by the processing circuitry  508 . Such machine readable instructions may be included on a computer readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon. The machine readable instructions may, for example, be executed by a general purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions of the processing circuitry  508  described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine readable instructions. Thus functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit, ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors. 
     Further, the teachings herein may be implemented in the form of a computer software product, the computer software product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure. 
     The present disclosure is described with reference to a flow chart. Although the flow diagram described above shows a specific order of execution, the order of execution may differ from that which is depicted. It shall be understood that each block in the flow chart, as well as combinations thereof can be realized by machine readable instructions. In some examples, at least some blocks may be carried out by the processing circuitry  508 . 
     Features described in relation to one example may be combined with features described in relation to any other example. 
     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. 
     The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. 
     The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.