Patent Publication Number: US-9849675-B2

Title: Protection device for ink-jet printhead

Description:
The present invention relates to a protection device for ink-jet printheads. 
     It is known that an ink-jet printer comprises at least one printhead from which ink droplets are emitted through nozzles and directed onto a medium to be printed. The printhead is movable relative to the medium through suitable actuating mechanisms and when it is not used is positioned in a service area installed on board the printer and therein carried by the actuating mechanisms themselves or, for longer periods of halt, it is dismantled and stowed in a storage container separated from the printer. The nozzles of the ink-jet printhead, when the printhead is in the service area of the printer or in the storage container, are kept in a bounded environment by means of a protection device comprising a rubber element referred to as “capping”. In the capping greater humidity than in the environment is generated, due to vaporisation of the water contained in the ink, and this prevents the printhead ink in the region close to the nozzles from drying. 
     For instance, document U.S. Pat. No. 6,293,648 discloses a protection device to be positioned under the printhead for sealingly closing and humidifying the printhead nozzles. The device comprises a housing body containing a liquid and having a plurality of apertures defined through an upper wall. Each aperture is provided with a seal for engagement against the printhead at a region surrounding one or more nozzles. A wick is inserted in each aperture and is partly dipped in the liquid. The liquid is transferred by capillarity from the wick to the apertures in such a manner that the space confined between the seals and the container is humidified. The device described in document U.S. Pat. No. 6,293,648 is further provided with a sealing film covering the apertures till the first use, when the film is to be removed and disposed of. 
     The Applicant has noticed that, when the devices of the known art as the one disclosed in document U.S. Pat. No. 6,293,648 are not associated with the printhead, i.e. when the printhead is printing, the liquid contained in the housing body is directly in communication with the external environment through said apertures and inevitably evaporates and is dispersed in the air. 
     The Applicant has further noticed that if the device is pulled out of the printer or of the storage container before the liquid inside it is used up, handling of it may give rise to unintentional leakage of the liquid. 
     The Applicant has found that the above mentioned drawbacks of the known art can be solved if protection device for ink-jet printheads is made, which protection device is provided with a tank for a humidifying liquid in which the opening designed to be associated with the printhead can be selectively and automatically closed or opened, in the absence or in the presence of the printhead respectively. 
     More specifically, according to a first aspect, the present invention relates to a protection device for ink-jet printheads comprising: a tank confining a cavity adapted to contain a humidifying liquid and having a mouth designed to be associated with at least one nozzle of an ink-jet printhead; a seal disposed around the mouth and able to be put sealingly in engagement against the printhead and around said at least one nozzle; characterised in that it comprises a mechanism integrated into the tank, for opening and closing said mouth for selectively bringing said mouth into fluid communication with the cavity. 
     The present invention, in at least one of the aforesaid aspects, can have one or more of the preferred features hereinafter described. 
     Preferably, the mechanism comprises a movable element installed on the tank and movable between a closing position of the mouth and an opening position of the mouth. 
     Preferably, said movable element is actuated from the closing to the opening positions by a pressure exerted against said movable element. 
     The mechanism is relatively simple, since the opening is controlled by the relative movement of the printhead pressing against the device. 
     Preferably, said movable element carries the seal. 
     It is the seal itself that, by exerting pressure against the printhead, determines displacement of the movable element. 
     Preferably, the mechanism comprises at least one spring interposed between said movable element and the tank and adapted to push said movable element to the closing position. 
     The automatic closure is obtained in a simple and efficient manner through use of the spring. 
     Preferably, the mechanism comprises a closure member fitted in the mouth; wherein in the open position said closure member together with the movable element confines a peripheral opening communicating with the cavity; wherein in the closing position said closure member has a first abutment surface in contact with a second abutment surface of the movable element. 
     The opening extends all around the nozzle or nozzles of the printhead and this geometric extension promotes a homogeneous humidification of the environment enclosed between said printhead and the protection device. 
     Preferably, the closure member is fastened onto the tank. 
     Preferably, the tank comprises a support extending in the cavity from a bottom wall of said tank to the mouth, and the closure member is fitted on one end of said support. 
     Preferably, the spring is a helical spring and is disposed around the support. 
     Due to the above features, the device is of simple construction. 
     Preferably, the device comprises a flexible wall, preferably made of rubber, connecting the movable element to peripheral edges of the tank. 
     Bending of the wall follows the movement of the movable element and at the same time ensures the hermetic tightness of the tank, preventing the liquid therein contained from evaporating. Preferably, the rubber wall is co-moulded with the seal and the movable plastic element, so as to create a hermetic seal and prevent vapour escape by leakage. In addition, preferably, the rubber wall is fastened to the peripheral edges of the container by a plastic frame co-moulded with the rubber wall and welded by ultrasonic waves to the container. 
     The rubber used for said wall must have a weak vapour-transmission coefficient to avoid water leakage therethrough. 
     Preferably, the overall evaporation rate of the protection device in the closed position is lower than 2 mg/day, preferably lower than 1.7 mg/day (measured with an ambient temperature of 22-25° C. and a relative humidity of 45-55%). 
     Preferably, the tank is made of Noryl™ SE1 GFN2 by SABIC. Preferably, the closure member is made of Novodur P2 H/AT 010555 by Ineos and, preferably, the rubber of the flexible wall is Santoprene™ 8191-55B100 by Exxon Mobil. 
     Preferably, according to an embodiment, the tank is filled with an hydrophilic composition (i.e. hydrophilic polymer) which, together with the humidifying liquid (i.e. water), forms an hydrogel composition provided with the same evaporation ratio of the liquid itself. The humidifying liquid is retained in the gel and also if the mouth of the device is open and the device overturned, no leakage of the liquid is permitted. 
     In a second aspect, the present invention relates to an ink-jet printer comprising at least one ink-jet printhead having at least one nozzle and at least one protection device in accordance with the above description. 
     Preferably, the protection device is movable between a first position, at which the mouth is spaced apart from the printhead nozzle, and a second position at which the mouth is associated with said nozzle; wherein in the first position the movable element is in the closing position of the mouth and in the second position the movable element is in the opening position of said mouth. 
     Preferably, the protection device comprises a projecting element, and wherein the printhead acts against said projecting element to take it from the first to the second positions. 
     The opening and closing movements of the protection device are controlled by the movement of the printhead. The device and printer therefore do not comprise motors specifically dedicated to opening or closing of the mouth of the protection device. The printer structure keeps unchanged as compared with the printers provided with protection devices of known type. The device according to the invention can apply to printers already on the market without any modification of same being required. 
     In a third aspect, the present invention relates to a servicing device for ink-jet printheads, comprising a supporting frame to be installed in an ink-jet printer and a protection device as above described. 
     Preferably, the protection device is movable on guides of the supporting frame between a first position, at which the mouth of the protection device is spaced apart from the printhead nozzle, and a second position at which the mouth is associated with said nozzle; wherein in the first position the movable element is in the closing position of the mouth and in the second position the movable element is in the opening position of said mouth. 
     The servicing device preferably also comprises a portion of absorbent material and a scraper element. The printhead, brought close to the servicing device, first passes on the portion of absorbent material, where ejection towards the absorbent material itself of the ink drops remained in the nozzles is operated, and subsequently on the scraper where the ink residues present on the nozzles are removed. 
     Preferably, the protection device is removably engaged on the frame of the servicing device. 
     In accordance with a fourth aspect, the present invention relates to an ink-jet printer comprising a servicing device as above described. 
     Preferably, the servicing device is installed on the printer in a removable manner. 
     The protection device or only the frame of the servicing device or the whole servicing device (comprising the protection device) can be easily extracted from the printer and replaced, usually together with the printhead. 
     Alternatively, the tank of the protection device can be refilled with the humidifying liquid and therefore its working lifetime is longer than that of the printhead and of the frame of the servicing device. The protection device will be extracted from the frame and housed in a new frame before being re-inserted in the printer with a new printhead. 
     In accordance with a fifth aspect, the present invention relates to a storage container for ink-jet printheads comprising at least one protection device as described above. 
     The storage container, known as “garage”, is a box separated from or integrated into the printer and capable of receiving one or more printheads for long periods of non-use of the latter. 
     In this case, the working lifetime of the protection device must substantially correspond to the working lifetime of the printer (several years). It is therefore preferable for the tank to be refilled a plurality of times. 
     Further features and advantages will become more apparent from the detailed description of a preferred but not exclusive embodiment of a servicing device for ink-jet printheads comprising a protection device in accordance with the present invention. 
    
    
     
       This description will be set out hereinafter with reference to the accompanying drawings, given by way of non-limiting example, in which: 
         FIG. 1  is a perspective view of a servicing device for ink-jet printheads comprising a protection device according to the present invention in a first position; 
         FIG. 2  shows the servicing device in  FIG. 1  with the protection device in a second position; 
         FIG. 3  is a cross-sectional view of the protection device in  FIG. 1  in a first operating configuration; 
         FIG. 4  is a cross-sectional view of the protection device in  FIG. 1  in a second operating configuration and associated with a printhead shown diagrammatically; 
         FIG. 5  is a first perspective view of a storage container or garage for ink-jet printheads; 
         FIG. 6  is a second perspective view of the storage container of  FIG. 5 . 
     
    
    
     With reference to the drawings, a servicing device for ink-jet printheads has been generally denoted at  1 . The servicing device  1  can be installed in a service area of an ink-jet printer (not shown) to which the printhead or printheads “H” are brought at the end of a printing cycle, preferably by the same mechanisms actuating them during printing, for carrying out cleaning operations and keep the nozzles “N” in an efficient condition. 
     The servicing device  1  comprises a supporting frame  2  that can be installed in a removable manner in the service area of the printer. Frame  2  has a housing for a protection device  3  for ink-jet printheads and further comprises a scraper element  4  and a portion of absorbent material  5 . In the embodiment shown, the scraper element  4  is interposed between the protection device  3  and the portion of absorbent material  5  and, when device  1  is fitted in the printer, the mentioned three components  3 ,  4  and  5  are aligned along a movement direction of the printhead “H”. 
     The housing is confined by two side walls  6  belonging to the frame  2  and each having a pair of guides  7  defined by grooves formed in said walls  6 . In greater detail, each groove  7  has a horizontal length  7   a  parallel to a reference plane, not shown, in which the surface of printhead “H” in which the printing nozzles are formed lies, and an oblique length  7   b  extending without a break from the horizontal length  7   a  to a base portion of frame  2 . The protection device  3 , described in detail in the following, has pins  8  each of which is fitted in a respective guide  7  in such a manner that they can slide therein. By its sliding in guides  7 , the protection device  3  is movable between a first lowered position and a second raised position. In the first lowered position ( FIG. 1 ), pins  8  lie at the ends of the oblique lengths  7   b  and device  3  is positioned at the base portion of frame  2 . In the second raised position ( FIG. 2 ), pins  8  lie at the ends of the horizontal lengths  7   a  and device  3  is spaced apart from the base portion of frame  2 . A return spring, not shown, retains the protection device  3  in the first lowered position, in the absence of external stresses. 
     The scraper element  4  is a flexible plate made of plastic or rubber for example, having one end mounted on frame  2  and the opposite end free. 
     The portion of absorbent material  5  consists of a porous material adapted to absorb the liquids and is housed in a suitable seat formed in frame  2 . When device  1  is mounted in the printer and the printhead “H” is in the service area, the free end of the scraper element  4  and the free surface of the absorbent material  5  are turned towards the nozzles “N” of said printhead “H”. 
     The protection device  3  comprises ( FIGS. 3 and 4 ) tank  9  of a cup-shaped structure preferably having a rectangular base and preferably made of plastic material. The tank internally delimits a cavity  9   a  adapted to contain a humidifying liquid “L” (water for example, possibly added with chemical bactericidal, fungicidal and the like agents). Two of the aforesaid pins  8  are positioned on each of two opposite side walls  10  of tank  9 . 
     Preferably, according to an embodiment, the cavity  9   a  is filled with an hydrophilic composition (i.e. hydrophilic polymer) which, together with the humidifying liquid “L”, forms an hydrogel composition provided with the same evaporation ratio of the liquid itself. 
     A support  12  of a cylindrical shape extends from a bottom wall  11  of tank  9 ; it is perpendicular to said bottom wall  11 . 
     The upper edges of tank  9  are connected to a flexible wall  13  made of rubber which partly closes the opening of tank  9  surrounded by said edges. 
     The flexible wall  13  at a central region thereof carries a movable element  14 . The movable element  14  comprises four side walls  14   a  delimiting a mouth  15  that can be selectively brought into fluid communication with cavity  9   a.    
     A seal  16  is disposed on the upper edges of the side walls  14   a  and it fully covers said side walls  14   a . An inner surface  16   a  of the seal  16  delimiting mouth  15  has an outwardly diverging portion, i.e. towards the printhead “H” when the latter is associated with the protection device  3 . Seal  16  forms a unitary piece with the flexible wall  13  and is preferably co-moulded with (or over-moulded to) the movable element  14 . The flexible wall  13  is further preferably co-moulded with (or over-moulded to) a frame  17  made of plastic material and in turn joined, preferably by ultrasonic wave welding, to the upper edges of tank  9 . The rubber material forming the flexible wall  13  and the seal  16  is suitable for co-moulding or over-moulding on the plastic material and has a weak vapour transmission coefficient. This rubber material is preferably Santoprene™ 8191-55B100 by Exxon Mobil. 
     Preferably, the tank  9  is made of Noryl™ SE1 GFN2 by SABIC. 
     Preferably, the overall evaporation rate of the protection device in the closed position is lower than 2 mg/day, preferably lower than 1.7 mg/day (measured with an ambient temperature of 22-25° C. and a relative humidity of 45-55%). 
     A helical spring  18  is disposed around the support  12  and has a first end in abutment against the bottom wall  11  of tank  9  and a second end, opposite to the first one, in abutment against a lower portion of the movable element  14 . 
     An upper end of the support  12  carries a closure member  19  shaped like a mushroom. The closure member  19  is secured to support  12  by means of a screw  20 . Preferably, the closure member  19  is made of Novodur P2 H/AT 010555 by Ineos. 
     The closure member  19  is placed in mouth  15  and is surrounded by the inner surface  16   a  of seal  16 . 
     The head of the closure member  19  has a first abutment surface  21  turned towards the bottom wall  11  and facing a second abutment surface  22  belonging to the inner surface  16   a  of seal  16 . 
     The movable element  14 , spring  18  and closure member  19  are part of an opening and closing mechanism of said mouth  15  integrated into tank  9 . 
     In the absence of external forces acting on the movable element  14 , spring  18  pushes and keeps the second abutment surface  22  belonging to seal  16 , against the first abutment surface  21  of the closure member  19  ( FIG. 3 ). The seal  16  is tightly fitted against the closure member  19  and the mouth  15  is closed, i.e. is not in fluid communication with the cavity  9   a  of tank  9 . 
     By a pressure exerted on an upper edge of seal  16 , the movable element  14  is pushed, against the action of spring  18 , in a movement direction along an X axis, towards the bottom wall  11  of tank  9 . The second abutment surface  22  is separated from the first abutment surface  21  and a passage is opened that brings mouth  15  into communication with the cavity  9   a  of tank  9  ( FIG. 4 ). This passage is defined by a peripheral opening  23  surrounding the head of the closure member  19 . If the force exerted on the upper edge of seal  16  stops, spring  18  recloses mouth  15  ( FIG. 3 ). 
     The yielding quality of the flexible wall  13  therefore must be capable of enabling lowering of the movable element  14  under the thrust action exerted by the printhead “H” and return to the closed position, due to the thrust of spring  18 . 
     The protection device  3  further comprises a projecting element  24  extending from tank  9  to the printhead “H” and has a surface  24   a  parallel to the movement direction axis X of the movable element  14 . This surface  24   a , when the protection device  3  is mounted on frame  2 , is turned towards the scraper element  4 . 
     In use, at the end of a printing cycle, the printhead “H” is brought to the service area wherein it is first stopped over the portion of absorbent material  5  and then operated for ejection of the ink drops entrapped in nozzles “N”. The protection device  3  is in the lowered position shown in  FIG. 1  and closed. 
     Subsequently, the printhead “H” is shifted towards the protection device  3  and passes on the scraper element  4  removing the ink residues present on nozzles “N”. 
     Going on moving, the printhead “H” or an element integral therewith impacts against the surface  24   a  and drags along the protection device  3  towards the second raised position shown in  FIG. 2  (in which figure, the printhead “H” being absent, the mouth  15  is represented in a closed position), against the action of the return spring. During this movement, seal  16  comes into contact with the printhead “H” and raising of the movable element  14  is stopped while the rest of the protection device  3  goes on raising, causing the relative movement between the movable element  14  and the closure member  19  and opening of mouth  15 . 
     The vapour inside tank  9  flows through the peripheral opening  23  filling the volume delimited by seal  16  and the printhead “H” ( FIG. 4 ), preventing the ink still present in nozzles “N” from drying. 
     When the printhead “H” has to print again, it is moved away from the service area, the return spring brings the protection device  3  back to the first position lowered on frame  2  and the movable element  14  pushed by spring  18  closes tank  9 . 
     The protection device  3  according to the invention is also applicable in a storage container  25  inside which the printheads “H” are positioned, after dismantling from the carriage moving them during printing, if they are not to be used for a long period of time. The storage container  25  is a box in which a housing  26  is formed for one or more printheads. In accordance with the present invention, the storage container  25  comprises one or more protection devices  3  located in suitable seats. When a printhead “H” is housed in the container  25 , it exerts a thrust action against the movable element  14  and opens mouth  15 , in the same manner as shown in  FIG. 4 . 
     The embodiment of the storage container  25  shown in  FIGS. 5 and 6  presents a cylindrical shape and is provided with a cover  27  covering one single housing  26  for a single printhead “H”. The storage container  25  comprises one single protection devices  3 . The mouth  15  of such a device  3  is visible, in  FIG. 6 , on the bottom wall of the housing  26 . 
     The storage container  25  further presents an access opening, not visible, covered by a movable lid  28  for refilling the tank of the device  3  which is part of the storage container  25 . The lid  28  can be opened by means of a push button  29 . The storage container  25  is also provided with an indicator  30  of the level of water contained inside the tank.