Patent Publication Number: US-2015072608-A1

Title: Method for forming an image

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for conditioning a recording medium storage enclosure in a printing system. The present invention further relates to a printing system comprising a printing station and a recording medium storage enclosure. The present invention further relates to an air flow kit for conditioning a recording medium storage enclosure. 
     BACKGROUND OF THE INVENTION 
     In a known method for conditioning a recording medium enclosure in a printing system a recording medium is provided in the form of a roll of an endless web wound on the reel inside a recording medium enclosure. The printing system further has a feeding path leading from the reel to a printing station for feeding a portion of the recording medium, a cutting device disposed at the feed path for cutting the web, and a feed control system. 
     In printers in which paper sheets or similar image receiving sheets are used as recording media, a tendency of the paper to cockle may occur. The cockling phenomenon is related to the fact that paper and similar materials tend to absorb humidity from ambient air and to expand and contract in accordance with their humidity content. When there exists a gradient in humidity within the paper, or any other non homogeneous state of humidity in the paper, then the more humid portion of the paper will expand more than the drier portion, which leads to the production of cockles or wrinkles. 
     In case the printing system terminates a print operation, a leading edge of the web, which has been cut after printing, is located in the feed path. Then, an end portion of the web that is present in the feed path inside the recording medium enclosure will be exposed to ambient air from both sides and can therefore absorb a large amount of moisture. 
     In order to reduce a moisture absorption by the end portion of the web the feed control system of the printing system is adapted to withdraw that end portion of the web onto the peripheral surface of the roll when the printing system is in a non-printing condition. When the print operation is continued, the web has to be feed again into the feed path, which needs a separating step for separating the leading edge from the surface of the roll, leading to a loss of productivity during resumption of the print operation. A gradient in humidity within the paper will still grow in time as the outer layer of the roll is exposed to ambient air, which will eventually lead to a higher humidity content of the leading end portion of the web. 
     SUMMARY OF THE INVENTION 
     In an aspect of the present invention, a method for conditioning a recording medium storage enclosure in a printing system is provided, which is capable of reducing effects of ambient air conditions on humidity conditions of a recording medium in a recording medium storage enclosure. 
     In a first aspect of the present invention a method for conditioning a recording medium storage enclosure in a printing system is provided, the recording medium storage enclosure comprising an exit opening being arranged at a first end of the recording medium storage enclosure, which exit opening is configured for releasing a portion of a recording medium towards a printing station of the printing system, the method comprising the steps of:
     a) providing an air flow inside the recording medium storage enclosure in a main air flow direction adjacent to the exit opening, wherein the main air flow direction is aligned along a direction of the exit opening, which is substantially perpendicular to a feeding direction of a recording medium through the exit opening;   b) circulating a first portion of the air flow provided in step a) within the recording medium storage enclosure between the first end and a second end of the recording medium storage enclosure opposite of the first end; and   c) directing a second portion of the air flow provided in step a) towards the exit opening in order to provide an overpressure inside the recording medium storage enclosure adjacent to the exit opening with respect to an ambient pressure outside the recording medium storage enclosure.   

     The recording medium storage enclosure is configured for storing a recording medium. The recording medium storage enclosure comprises an exit opening, which is arranged at a first end of the recording medium storage enclosure. A shape of the exit opening is suitably selected for guiding a portion of the recording medium from inside the recording medium storage enclosure outward. The recording medium storage enclosure may be substantially closed, and may be partially closed. Preferably the recording medium storage enclosure is for the most part closed. Openings in the recording medium storage enclosure are possible in so far as these openings do not prohibit the circulation of a portion of the air flow in the recording medium storage enclosure. 
     In the air flow step a) an air flow is provided inside the recording medium storage enclosure in a main air flow direction adjacent to the exit opening. The main air flow direction is the predominant flow direction of the air flow. The air flow is provided in the main air flow direction adjacent to the exit opening in order to minimize a flow of ambient air through the exit opening. Attributes of the air flow, such as a flow rate and a distance between the main air flow direction and the exit opening, may be suitably selected. The main air flow direction is aligned along a direction of the exit opening, which is substantially perpendicular to a feeding direction of a recording medium through the exit opening. As a result an air flow through the exit opening is minimized. 
     It has been found that the feeding direction of the recording medium is usually a most sensitive direction towards an air flow through the exit opening. In case a different direction of the exit opening is more sensitive, the main air flow may suitably be adapted, such that it is perpendicular to the more sensitive direction of the exit opening. In a circulating step b) a first portion of the air flow, which is provided in the main air flow direction, is circulated between the first end and the second end of the recording medium storage enclosure opposite of the first end. Circulating the first portion of the air flow means that the first portion is moved from the first end to the second end of the recording medium storage enclosure, and sub sequently is moved back from the second end to the first end of the recording medium storage enclosure. Means may be provided in the recording medium storage enclosure for supporting the circulation of the first portion of the air flow between the first end and the second end (e.g. air flow ducts, air flow distribution means, etc). 
     The first portion of the air flow enhances that a micro climate inside the recording medium storage enclosure is made uniform. The micro climate is a local atmospheric zone within the recording medium storage enclosure where the climate differs from the surrounding area of the recording medium storage enclosure. For example in case the humidity of the air at the first end of the recording medium storage enclosure is higher than the humidity of the air at the second end of the recording medium storage enclosure, the circulating first portion of the air flow reduces the difference in humidity of the air of the first end and the second end of the recording medium storage enclosure. 
     In an exit directing step c) a second portion of the air flow, which is provided in the main air direction, is directed towards the exit opening in order to provide an overpressure inside the recording medium storage enclosure adjacent to the exit opening with respect to an ambient pressure outside the recording medium storage enclosure. The second portion of the air flow further prohibits ambient air from entering the recording medium storage enclosure through the exit opening. The second portion of the air flow may affect the remaining air pressure inside recording medium enclosure away from the exit opening. The second portion of the air flow is suitably selected such that the air pressure inside recording medium enclosure away from the exit opening is decreased little, in order that not too much air is sucked in the recording medium storage enclosure at a position away from the exit opening. 
     As a result the air conditions inside the enclosure are equalized (i.e. an uniform microclimate is provided) while at the same time ambient air conditions are kept outside of the enclosure. As a result of the uniform microclimate inside the recording medium storage enclosure a gradient in humidity within the paper may also be reduced by the present method leading to a reduction of cockling of the paper. 
     In an embodiment of the method, step a) further comprises aligning the main air flow direction along a feed path of the recording medium, which feed path is configured for conveying the recording medium towards the exit opening. A leading edge of the recording medium may be retained, after termination of the print operation, in the feed path close to the exit opening. By aligning the main air flow direction of step a) along the feed path of the recording medium, the air in the feed path is circulated within the recording medium storage enclosure during step b). Furthermore, in case a leading edge of the recording medium is present in the feed path, the conditioning of the leading end portion of the recording medium is optimized and the leading end portion is protected from ambient air conditions. A feed path may comprise several guiding plates for conveying the recording medium towards the exit opening. The main air flow direction may be aligned with a surface of one of the guiding plates. 
     In an embodiment of the method, the first portion of the air flow of step b) is larger than the second portion of the air flow of step c). The circulating first portion provides an uniform microclimate and the exit directed second portion provides an overpressure adjacent to the exit opening with respect to an ambient pressure outside the recording medium storage enclosure. The first portion being larger than the second portion provides that an uniform microclimate can be attained faster. The exit opening may be suitably configured, such that a second portion of the air flow is sufficient to prohibit ambient air from entering the recording medium storage enclosure through the exit opening. 
     In an embodiment of the method, the air of the air flow provided in step a) is pre-heated above ambient air temperature prior to step a). Pre-heated air inside the recording medium storage enclosure provides that an overall air pressure inside the recording medium storage enclosure adjacent to the exit opening increases, thereby even further prohibiting ambient air from entering the recording medium storage enclosure through the exit opening. Furthermore the pre-heated air reduces a humidity of a recording medium during circulation step b). In case a leading edge has been exposed to humid ambient air outside of the recording medium storage enclosure, a resulting gradient in humidity within the recording medium is reduced faster during conditioning inside the recording medium storage enclosure. 
     In an embodiment of the method, the air of the air flow provided in step a) is dehumidified with respect to an ambient air humidity prior to step a). The dehumidified air reduces a humidity of a recording medium during circulation step b). In case a leading edge has been exposed to humid ambient air outside of the recording medium storage enclosure, a resulting gradient in humidity within the recording medium is reduced faster during conditioning inside the recording medium storage enclosure. 
     In an embodiment of the method, the method further comprises step d) feeding a portion of the recording medium through the exit opening of the recording medium storage enclosure towards the print station of the printing system, and wherein step a) is performed after step d) has ended. A tendency of the recording medium to cockle is further reduced, in case the air flow is provided during a retraction movement of the leading edge into the recording medium storage enclosure and in case the air flow is provided during a first period directly after a termination of the print operation. 
     In another aspect of the present invention a printing system is provided, which comprises a printing station and a recording medium storage enclosure, wherein the recording medium storage enclosure comprises:
     a) an exit opening arranged at a first end of the recording medium storage enclosure for releasing a portion of a recording medium towards the printing station of the printing system;   b) an air flow source for providing a circulating air flow inside the recording medium storage enclosure between the first end and the second end of the recording medium storage enclosure opposite of the first end;   c) an air flow manifold for directing the air flow at the first end of the recording medium storage enclosure in a main air flow direction adjacent to the exit opening, wherein the main air flow direction is aligned along a direction of the exit opening, which is substantially perpendicular to a feeding direction of a recording medium through the exit opening; and   d) a distribution means arranged at the first end for directing a circulating first portion of the air flow from the first end to the second end of the recording medium storage enclosure and directing a second portion of the air flow towards the exit opening in order to provide an overpressure inside the recording medium storage enclosure adjacent to the exit opening with respect to an ambient pressure outside the recording medium storage enclosure,
 
the printing system further comprises a control unit for controlling the air flow source. The air flow source may be an air pump, or any other means to provide an air flow. The air flow manifold is arranged at the first end of the recording medium storage enclosure in order to direct the air flow in the main air flow direction adjacent to the exit opening. The air flow manifold may suitably be configured to adjust attributes of the air flow, such as a flow rate and a distance between the main air flow direction and the exit opening. In an embodiment the air flow manifold may be configured to provide an air curtain along a direction of the exit opening. An air curtain is an air flow in the main air flow direction, which covers a substantially complete area of the exit opening perpendicular to a feeding direction of a recording medium through the exit opening (e.g. covers a height of the exit opening).
   

     In an embodiment of the printing system, the air flow manifold is arranged for aligning the main air flow direction along a feed path configured for conveying the recording medium towards the exit opening. By aligning the main air flow direction of step a) along the feed path of the recording medium, the air in the feed path is circulated within the recording medium storage enclosure during step b). 
     In an embodiment of the printing system, the printing system further comprises a sensor for sensing an ambient air condition and wherein the control unit controls the air flow source based on a sensor signal provided by the sensor to the control unit indicating the ambient air condition. This improves the conditioning of the recording medium storage enclosure. For example a flow rate of the air flow may be adapted based on one or more of the conditions of an ambient air pressure and a humidity of the ambient air. 
     In an embodiment of the printing system, the recording medium storage enclosure further comprises a duct arranged for channeling the air flow from the second end of the recording medium storage enclosure towards the air flow manifold. This supports the circulating step b). The duct may be connected to the air flow manifold and may be connected to the air flow source. The duct may be a channel, may be a tube, may be a hollow cylinder and may be any other means for channeling the air flow from the second end of the recording medium storage enclosure towards the air flow manifold. 
     In an embodiment of the printing system, the recording medium storage enclosure further comprises a recording medium supporting means for supporting the recording medium, being arranged between the first end and the second end of the recording medium storage enclosure. The recording medium supporting means may be suitably arranged inside the recording medium storage enclosure in order to support the circulating step b). 
     In an embodiment of the printing system, recording medium storage enclosure further comprises a feed control system for in operation feeding a portion of the recording medium in the recording medium storage enclosure towards the printing station of the printing system, and wherein the control unit controls the air flow source based on the feeding operation by the feed control system. A reduction of the recording medium to cockle is further optimized, in case the air flow is provided based on the feeding operation by the feed control system. For example during a retraction movement of the leading edge into the recording medium storage enclosure and in case the air flow is provided during a first period directly after a termination of the feeding operation. 
     In another aspect of the present invention an air flow kit is provided for conditioning a recording medium storage enclosure, the recording medium storage enclosure comprising an exit opening for releasing a portion of a recording medium towards the printing station of the printing system, wherein the air flow kit comprises:
     a) an air flow source for providing a circulating air flow inside the recording medium storage enclosure between a first end of the recording medium storage enclosure adjacent to the exit opening and a second end of the recording medium storage enclosure opposite of the first end;   b) an air flow manifold for directing the air flow at the first end of the recording medium storage enclosure in a main air flow direction adjacent to the exit opening;   c) a distribution means for directing a circulating first portion of the air flow from the first end to the second end of the recording medium storage enclosure and directing a second portion of the air flow towards the exit opening in order to provide an overpressure inside the recording medium storage enclosure adjacent to the exit opening with respect to an ambient pressure outside the recording medium storage enclosure; and   d) a duct for channeling the air flow from the second end of the recording medium storage enclosure towards the air flow manifold.   

     The air flow kit may be suitably arranged inside a recording medium storage enclosure in order to provide a method for conditioning the recording medium storage enclosure according to the present invention. The air flow source is arranged in the circulating air flow path between the first end and the second end of the recording medium storage enclosure. 
     The air flow manifold is arranged close to the exit opening, wherein the arrangement is suitable to direct the air flow in a main air flow direction adjacent to the exit opening. The distribution means is arranged along the main air flow direction close to the exit opening. The distribution means may be arranged at any position with respect to the exit opening along the main air flow path; for example preceding the exit opening, next to the exit opening or subsequently to the exit opening in the main air flow direction. The distribution means may be connected to the air flow manifold. 
     The duct is arranged between the second end and the air flow manifold at the first end of the recording medium storage enclosure. The duct may be connected to the air flow manifold and may be connected to the air flow source. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Hereinafter, the present invention is further elucidated with reference to the appended drawings showing non-limiting embodiments and wherein 
         FIG. 1A  shows a schematic vertical cross-section of a paper transport system of an ink jet printer; and 
         FIG. 1B  is an enlarged schematic view of a prior art recording medium storage enclosure. 
         FIG. 2A  shows a schematical plan view of a recording medium storage enclosure according to a first embodiment of the present invention. 
         FIG. 2B  shows a schematical cross section view of the recording medium storage enclosure along the line D-D of the embodiment of  FIG. 2A . 
         FIG. 2C  shows an enlarged view of the distribution means of the first embodiment shown in  FIG. 2A . 
         FIG. 3  shows a schematical plan view of a recording medium storage enclosure according to a second embodiment of the present invention. 
         FIG. 4A  shows a schematical plan view of a recording medium storage enclosure according to a third embodiment of the present invention. 
         FIG. 4B  shows a schematical cross section view of the recording medium storage enclosure along the line D-D of the embodiment of  FIG. 4A . 
         FIG. 5A  shows a schematical side view of a recording medium storage enclosure according to a fourth embodiment of the present invention. 
         FIG. 5B  shows a schematical plan view of the recording medium storage enclosure along the line D-D of the embodiment of  FIG. 5A . 
         FIG. 6  shows a flow-chart of a method according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views. 
     As is shown in  FIG. 1A , an ink jet printer comprises a frame  10  (which has only been shown in phantom lines) and which accommodates a paper storage unit  11  and a paper feed system  14  adapted to feed a sheet  16  of paper to a printing station  18  on the top side of the frame  10 . In the printing station  18 , the sheet  16  is moved over a sheet support plate  20 . A carriage  22  is arranged to travel back and forth across the sheet  16  in the direction normal to the plane of the drawing in  FIG. 1A  and carries at its bottom side a number of ink jet print heads  24  facing the sheet  16 . Thus, by energising the print heads  24 , a swath of an image is printed in each pass of the carriage  22 . Then, the sheet  16  is advanced by a step of appropriate length in a direction indicated by an arrow X, so that the next swath can be printed. A discharge mechanism  26  discharges the sheet onto a tray  28  which, in the example shown, accommodates already a printed sheet  30 . 
     The paper storage unit  11  comprises one recording medium storage enclosure  12 , accommodating a reel  32  and two larger recording medium storage enclosures  13  for accommodating two reels  32 , each reel providing a supply of printing paper in the form of a paper roll  33 . In each recording medium storage enclosure a web  34  is drawn-off from each paper roll  33  by means of an associated pair of transport rollers  36 . Each of the recording medium storage enclosures  12 ,  13  comprises narrow feed paths  40 , which merge into a common transport path  42  on the top side of the paper storage unit  11 . The pairs of transport rollers  36  are selectively driven to feed the web  34  from a selected one of the reels  32  in one of the recording medium storage enclosures  12 , 13  to the common transport path  42 . It will be understood that the reels  32  may contain paper of different qualities and possibly also non-paper recording media such as plastic films or the like. Further, the webs on the reels  32  may differ in width, so that printed sheets may be produced in different formats, ranging for example from A4 portrait to A0 landscape. With the phrase “endless web  34 ” it is meant that the length of paper on reels  32  is long compared to the cutted sizes A4 or A0. Typically the length of such a web is between 20 and 200 meters but can be also longer than that. 
     From the common transport path  42 , the selected web is guided past a cutting mechanism  44  for cutting the web to the desired sheet length. 
     On its way from the reel  32  to the sheet support plate  20 , the web  34  and the sheet  16 , respectively, will be exposed to ambient air and, as a result, will absorb humidity, especially when the relative humidity RH of the ambient air is high. 
     When the humidity content of the paper increases, it tends to expand. Typically, the paper expands in the direction transverse to the longitudinal direction of the web. When the sheet  16 , after having expanded in this way, reaches the sheet support plate  20 , part of the water contained in the paper will be evaporated, and the paper shrinks again in width direction of the sheet. Thus, since a humidity gradient is present in the paper, the accompanying expansion in width of the sheet leads to the production of cockles. 
       FIG. 1B  is an enlarged schematic view of a prior art recording medium storage enclosure shown in  FIG. 1A . In  FIG. 1B  the recording medium storage enclosure  12  is shown, which accommodates a reel  32  for providing a supply of printing paper in the form of an endless web  34 . Recording medium storage enclosure  12  comprises an exit opening  60  at a first end  12   a  of the recording medium storage enclosure for releasing a portion of a recording medium towards the printing station of the printing system. An arrangement of guide plates  38  defines the feed path  40 . In  FIG. 1B  it is shown that the recording medium storage enclosure  12  is capable of withdrawing a web  34 , that has been fed into the feed path  40 , back onto the roll  33  on the reel  32  from which it had been drawn-off. Each of the reels  32  is independently driven by an electric motor, which has not been illustrated, and may rotate in either direction under the control of an electronic feed control system  46  ( FIG. 1A ), as has been symbolized by dashed lines  47  for the upper reel  32  in  FIG. 1A . 
     The feed control system  46  is also connected to a humidity sensor  48 . Further, the feed control system  46  is connected to a separating mechanism  49  ( FIG. 1B ) that is arranged at the periphery of each of the reels  32  at a position where the web  34  is drawn off from the roll  33 . 
       FIG. 1B  illustrates a condition where a web  34 , which has been drawn off from a paper roll  33  on the reel  32 , has just been cut by means of the cutting device  44 , so that the leading edge  35  of the web is located in the paper feed path  40  near the exit opening  60  of the recording medium storage enclosure. When, at that instant, a new print job has already been programmed, and this print job specifies that the recording medium shall be the same web  34  that is already in the feed path, then the web  34  will be fed further towards the print station  18  as indicated by arrow S. 
     On the other hand, if no new print job is in the print queue, the leading edge  35  of the web may be retained in the paper feed path  40  near the exit opening  60  of the recording medium storage enclosure. However ambient air is able to enter the recording medium storage enclosure  12  through the exit opening  60  as is indicated by arrow A. As a result a gradient of humidity may develop in the recording medium storage enclosure between a first end  12   a  of the recording medium storage enclosure, where the exit opening  60  is arranged, and a second end  12   b  of the recording medium storage enclosure. This causes the leading edge  35  of the web, being arranged in the paper feed path  40 , to be exposed to a relatively high humidity and a peripheral surface of the roll  33   b  to be exposed to a relatively low humidity. 
     Alternatively, in case the feed control system  46  reads the air humidity that has been detected by the sensor  48 , and if the air humidity is above a certain threshold level, the reel  32  is driven in reverse direction, as is indicated by an arrow Rr in  FIG. 1B , so as to withdraw the web  34  from the paper feed path  40 , as indicated by arrow R in  FIG. 1B , and back onto the periphery of the roll  33 . The rotation of the reel  32  will be stopped when it is detected that the leading edge  35  of the web has reached the position of the separating device  49 . Thus, the entire length of the web  34  is stored in a compacted state in the roll  33 . 
     Also when the entire length of the web  34  is stored in a compacted state in the roll  33 , a gradient of humidity inside the recording medium storage enclosure may grow, which causes a portion  33   a  of the peripheral surface of the roll, being arranged near the first end  12   a  of the recording medium storage enclosure, to be exposed to a relatively high humidity and a portion  33   b  of the peripheral surface of the roll to be exposed to a relatively low humidity. 
     Furthermore when a new print job is entered, the printer is again switched into the printing operating mode, and the feed control system  46  controls the reel  32  to rotate in feed direction, as has been indicated by an arrow Sr. Simultaneously, the separating mechanism  49  is activated so as to separate the leading edge of the web from the periphery of the roll  33 , e.g. by air suction. The separation of the leading edge from the periphery of the roll  33  requires time and the feeding of the leading edge towards the exit opening  60  of the recording medium storage enclosure is delayed. 
       FIG. 2A  shows a schematical plan view of a recording medium storage enclosure according to a first embodiment of the present invention. In a recording medium storage enclosure  12  a paper roll  33  is supported by a reel  32 , wherein a web  34  is drawn-off from the paper roll  33  by means of a respectively associated pair of transport rollers  36  and fed in a feeding direction S through the feeding path  40  towards an exit opening of the recording medium storage enclosure  60 . A leading edge of the web  35  is positioned adjacent to the exit opening  60 . 
     In the recording medium storage enclosure  12  an air flow manifold  54  is arranged at the first end of the recording medium storage enclosure  12   a.  The air flow manifold  54  is operatively connected to a duct  58 , which is operatively connected to an air flow source  56 . The air flow source  56  is controlled by a control unit  2  (shown in  FIG. 2B ). In operation condition the air flow source  56  provides an air flow P along the duct  58  towards the air flow manifold  54 . The air flow manifold  54  directs the air flow in a main air flow direction M adjacent to the exit opening  60 , wherein the main air flow direction M is aligned substantially perpendicular to the feeding direction S of the web  34  through the exit opening  60 . Attributes of the air flow M, such as a flow rate, flow velocity and a distance between the main air flow M and the exit opening  60 , are suitably selected in order to extend the air flow M over substantially the width of the exit opening W. A distribution means  59  (also shown in  FIG. 2C ) is arranged at the first end  12   a  of the recording medium storage enclosure in the main air flow M. The distribution means directs a first portion F 1  of the air flow M towards the second end of the recording medium storage enclosure  12   b  in order to circulate the first portion F 1  between the first end  12   a  and the second end  12   b  of the recording medium storage enclosure (as is indicated by arrows F 1 ). The circulation of the first portion F 1  between the first end  12   a  and the second end  12   b  is enhanced by the arrangement of the air flow source  56  at the second end  12   b  of the recording medium storage enclosure. The distribution means  59  further directs a second portion F 2  of the air flow M towards the exit opening  60 . The second portion F 2  provides an overpressure inside the recording medium storage enclosure  12  adjacent to the exit opening  60  with respect to an ambient pressure outside the recording medium storage enclosure. 
     The first portion F 1  of the air flow provides that a micro climate, which is inside the recording medium storage enclosure  12 , is made uniform. In case the humidity of the air at the first end of the recording medium storage enclosure  12   a  is higher than the humidity of the air at the second end  12   b  of the recording medium storage enclosure, the circulating first portion F 1  of the air flow reduces a difference in humidity of the air between the first end and the second end of the recording medium storage enclosure. As a result a leading edge  35  of the web, which is arranged inside the paper feed path  40  close to the first end  12   a  of the recording medium storage enclosure, will have a similar humidity compared to a peripheral surface portion  33   b  of the roll, which is arranged close to the second end  12   b  of the recording medium storage enclosure. 
       FIG. 2B  shows a cross-sectional view of the recording medium storage enclosure along the line D-D of the embodiment of  FIG. 2A . In  FIG. 2B  it is shown that the air flow source  56  is arranged at a lower side of the recording medium storage enclosure  12  at the second end  12   b  of the recording medium storage enclosure, while the air flow manifold  54  is arranged at an upper side of the recording medium storage enclosure  12  near the first end  12   a  of the recording medium storage enclosure. This arrangement of both the air flow source  56  and the air flow manifold  54  enhance the circulation of the air flow throughout the recording medium storage enclosure  12 . Further it is shown that the air flow manifold  54  is arranged with respect to the paper feed path  40 , such that the main air flow direction M is aligned with a lateral direction of the feed path  40  of the recording medium. In fact in  FIG. 2B  the air flow M is directed parallel to a common plane of the respectively associated pair of two guiding plates  38   a,    38   b,  which enclose the feed path  40 . A leading edge  35  of the web is arranged inside the feed path  40  close to the exit opening  60 . The main air flow M is arranged inside the feed path  40  at one side of the web  34 . It has been found that an air flow M at one side of the web  34  is sufficiently effective in reducing a gradient in humidity of the web  34 . Alternatively the main air flow M may be arranged at both sides of the leading edge  35  of the web. 
       FIG. 2C  illustrates an enlarged view of the distribution means of the first embodiment shown in  FIG. 2A . The distribution means  59  comprises a plurality of grooves  61  distributed along the main air flow M path. The plurality of grooves  61  directs a first portion F 1  of the air flow towards the second end  12   b  of the recording medium storage enclosure. Furthermore the distribution means  59  comprises a plate having plurality of openings  63  distributed along the main air flow M path adjacent to the exit opening  60 . The plurality of openings  63  directs a second portion F 2  of the air flow towards the exit opening  60 . Alternatively a distance between the guiding plate  38   a  and the guiding plate  38   b  may suitably be selected (shown in  FIG. 2B ) in order to direct a second portion F 2  of the air flow towards the exit opening  60 . 
       FIG. 3  shows a schematical plan view of a recording medium storage enclosure according to a second embodiment of the present invention. In  FIG. 3A  the recording medium storage enclosure  312  is shown. In the recording medium storage enclosure  312  a first air flow manifold  354  and a second air flow manifold  364  are arranged at opposite sides, respectively, of the first end  312   a  of the recording medium storage enclosure. The first air flow manifold  354  is operatively connected to a first duct  358 , which is operatively connected to a first air flow source  356 . The second air flow manifold  364  is operatively connected to a second duct  368 , which is operatively connected to a second air flow source  366 . 
     The first air flow source  356  and the second air flow source  366  are controlled by a control unit (not shown). In operation condition the first and second air flow source  356 ,  366  provide an air flow P 1 , P 2  along the duct  358 ,  368  towards the air flow manifold  354 ,  364 , respectively. The first and second air flow manifold  354 ,  364  are configured to provide an air flow in a first and second main air flow direction M 1 , M 2 , respectively, adjacent to the exit opening  60 . The first and second main air flow direction M 1 , M 2  are both aligned substantially perpendicular to the feeding direction S of the web  34  through the exit opening  60 . The first main air flow direction M 1  is arranged substantially opposite to the second main air flow direction M 2 , such that two main air flow directions encounter each other adjacent to the exit opening  60 . Due to the interaction between the first and the second main air flow direction M 1 , M 2 , a first circulating portion D 1 , E 1  of each of the air flows M 1 , M 2  is directed towards the second end of the recording medium storage enclosure  312   b.  Likewise a second portion D 2 , E 2  of each of the air flows M 1 , M 2  is directed towards the exit opening  60 . The second portion D 2 , E 2  provides an overpressure inside the recording medium storage enclosure  312  adjacent to the exit opening  60  with respect to an ambient pressure outside the recording medium storage enclosure. The ratio between the volume of each of the first portions D 1 , E 1  and each of the second portions D 2 , E 2  may suitably be adjusted, e.g. by adjusting the attributes of the first and second main air flow direction M 1 , M 2 . 
       FIG. 4A  shows a schematical plan view of a recording medium storage enclosure according to a third embodiment of the present invention. In  FIG. 4A  the recording medium storage enclosure  412  is shown. In the recording medium storage enclosure  412  a first air flow manifold  454  and a second air flow manifold  464  are arranged at the first end of the recording medium storage enclosure  412   a  below a feed path  40 . The first air flow manifold  454  is operatively connected to a first air flow source  456 , which is operatively connected to a first duct  458 . The second air flow manifold  464  is operatively connected to a second air flow source  466 , which is operatively connected to a second duct  468 . An inlet portion of the first and second ducts  459 ,  469 , respectively, is arranged at opposite sides, respectively, of a second end  412   b  of the recording medium storage enclosure. 
     The first and second air flow sources  456 ,  466  are controlled by a control unit  2  (shown in  FIG. 4B ). In operation condition the first and second air flow source  456 ,  466  provide an air flow P 3 , P 4  along the duct towards the air flow manifolds  454 ,  464 , respectively. The first and second air flow manifold  454 ,  464  are configured to direct an air flow in a first and second main air flow direction M 3 , M 4 , respectively, adjacent to the exit opening  60  (in the direction normal to the plane of  FIG. 4A ). The main air flow directions M 3 , M 4  are both aligned substantially perpendicular to the feeding direction S of the web  34  through the exit opening  60 . The first main air flow direction M 3  is arranged substantially parallel to the second main air flow direction M 4 . The first and second main air flow direction M 3 , M 4  extend over a part of the width of the exit opening W 1 , W 2 , respectively. The parts of the width W 1 , W 2  are suitably selected in order to cooperatively cover a sufficient part of the width of the exit opening W. 
       FIG. 4B  shows a cross-sectional view of the recording medium storage enclosure along the line D-D of the embodiment of  FIG. 4A . A leading edge  35  of the web is positioned in the feed path  40  adjacent to the exit opening  60 . Both first and second main air flow direction M 3 , M 4  are directed towards a lower side of the feed path  40 , thereby encountering a lower side of the leading edge  35  of the web. Attributes of the feed path  40 , such as an open structure, is suitably selected to direct a circulating first portion G 1  between the first end  412   a  and the second end  412   b  of the recording medium storage enclosure and to direct a second portion G 2  towards the exit opening  60 . Furthermore a position of the leading edge  35  of the web in the feed path  40  may be adjusted in order to adjust a ratio in volume between the first portion G 1  and the second portion G 2 . For example, the leading edge  35  of the web may be positioned closer to the exit opening, thereby reducing the volume of the first portion G 1  and increasing the volume of the second portion G 2 . 
       FIG. 5A  shows a schematical side view of a recording medium storage enclosure according to a fourth embodiment of the present invention. In a cut sheet recording medium storage enclosure  80  a stack of cut sheets  83  is supported by a sheet loading plate  82 . The stack of sheets  83  is aligned at two sides, each side being confined by a sheet side restriction  81   a,    81   b  (the latter only being shown in  FIG. 5B ). The sheet loading plate  82  is lifted at a first end  80   a  of the recording medium storage enclosure by a lifter plate  84 . The sheet loading plate  82  is rotatably supported at a second end  80   b  of the recording medium storage enclosure by a rotatable shaft  88 . The lifter plate  84  is rotatably supported by a lifter drive shaft  86 , which is rotated by a lifter drive gear  87 . The lifter plate  84  is positioned such that an upper cut sheet of the stack of sheets  83   a  is moved into contact with a pick upper roller  90 . The pickup roller  90  is rotatably driven to feed the upper cut sheet of the stack of sheets  83   a  in a feeding direction, as indicated by arrow S, towards an exit opening  94  of the recording medium storage enclosure  80 , which is arranged at the first end  80   a  of the recording medium storage enclosure. 
       FIG. 5B  shows a plan view of the recording medium storage enclosure along the line D-D of the embodiment of  FIG. 5A . In the recording medium storage enclosure  80  a first air flow manifold  545  and a second air flow manifold  565  are arranged at opposite sides, respectively, of the first end  80   a  of the recording medium storage enclosure. The first air flow manifold  545  is operatively connected to a first duct  558 , which is operatively connected to a first air flow source  556 . The second air flow manifold  565  is operatively connected to a second duct  568 , which is operatively connected to a second air flow source  566 . 
     The first air flow source  556  and the second air flow source  566  are controlled by a control unit (not shown). In operation condition the first and second air flow source  556 ,  566  provide an air flow P 1 , P 2  along the duct  556 ,  566  towards the air flow manifold  545 ,  565 , respectively. The first and second air flow manifold  545 ,  565  are configured to direct the air flow in a first and second main air flow direction M 1 , M 2  adjacent to the exit opening  94 , wherein the main air flow direction M 1 , M 2  are both aligned substantially perpendicular to the feeding direction S of an upper cut sheet  83   a  through the exit opening  94 . Each of the main air flow directions M 1 , M 2  is aligned with a surface of the upper cut sheet  83   a.    
     The first main air flow direction M 1  is arranged opposite to the second main air flow direction M 2 , such that two main air flow directions encounter each other adjacent to the exit opening  94 . 
     Due to the interaction between the first and the second main air flow direction M 1 , M 2 , a first circulating portion D 1 , E 1  of each of the air flows M 1 , M 2  is directed towards the second end  80   b  of the recording medium storage enclosure. Likewise a second portion D 2 , E 2  of each of the air flows M 1 , M 2  is directed towards the exit opening  94 . The second portion D 2 , E 2  provides an overpressure inside the recording medium storage enclosure  12  adjacent to the exit opening  94  with respect to an ambient pressure outside the recording medium storage enclosure. The ratio between the volume of each of the first portions D 1 , E 1  and each of the second portions D 2 , E 2  may suitably be adjusted, e.g. by adjusting the attributes of the first and second main air flow direction M 1 , M 2 . 
       FIG. 6  shows a flow-chart of a method according to the present invention. The method illustrated here can be used in any of the first, second, third and fourth embodiments of the present invention (as shown in  FIG. 2A-5B ). The steps of the method will be explained for a web based recording medium. The steps may be performed likewise for a stack of cut sheets. 
     In step S 2  of the method it is judged whether a print operation is terminated. In case yes in step S 4  a feed operation of the web is ended and the leading edge is retracted to the feed path  40  in the recording medium storage enclosure. In step S 6  at least one attribute of the ambient air condition is determined, such as an ambient air pressure, an ambient air humidity and an ambient air temperature. The ambient air condition may be obtained from a sensor, such as humidity sensor  48 . In step S 8  a volume of a first circulating portion and a second portion is determined by a control unit based on the determined ambient air condition of step S 6 . In step S 10  an air flow source is operated by the control unit in order to provide an air flow based on the volume of the first and second portion determined in step S 8 . In step S 12  it is judged whether the ambient air humidity is high with respect to a threshold value, based on a determined ambient air condition of step S 6 . In case yes, in step S 14  the air flow, which is provided by the air flow source inside the recording medium storage enclosure, is pre-heated or dehumidified. In step S 16  the air flow is provided, inside the recording medium storage enclosure, wherein a first portion of the air flow is circulated and a second portion of the air flow is directed to the exit opening of the recording medium storage enclosure. Optionally, in case desired, a ratio between the volume of the first portion and the second portion may be adjusted in an additional step (not shown in  FIG. 6 ), in the way as is described in the second and third embodiments. In step S 18  it is judged whether a new print operation is started. In case yes, in step S 20  the air flow in the recording medium storage enclosure is terminated by inactivating the air flow source and a leading edge of the web is transported through the exit opening towards the printing station. In case no, the steps S 6 -S 18  are repeated. 
     Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination and any advantageous combination of such claims is herewith disclosed. 
     Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.