Abstract:
An inkjet printer has a print bar system comprising a print bar and a plurality of selectively replaceable print heads attached to the print bar. The system comprises a receptor on the bar, for installation of a print head, each print head having a rear face for insertion in said receptor in a first direction. A latch is provided, pivoted on the bar. The latch has a user-actuatable handle adapted, during a first movement thereof, to engage a latch member of the latch with a catch on the bar to lock the latch in a lockable position on the bar. A platform is mounted on the latch with freedom to move with respect to the latch in said first direction when the latch is in said lockable position. The platform has a latch electrical connector, adapted to engage a head electrical convector on the print head, by mutual movement of the connectors in said first direction. A bias means urges the platform in said first direction. A second movement of the handle releases the platform for movement relative to the latch under the action of the bias means. When the latch is in the lockable position, and the print head is installed in the receptor, the first movement of the handle locks the latch in the lockable position and the second movement of the handle releases the platform so that the bias means presses the platform in said first direction to engage said electrical connectors and urge the print head into secure engagement with the receptor.

Description:
BACKGROUND 
       [0001]    On a print bar of a page-wide array ink-jet printer, a plurality of print heads are usually disposed in side-by-side relation, each of which is generally arranged to be consumer-replaceable. An electronics connection is required between the printer (the print bar) and the print head. At the same time, the print head requires a fluid connection to transport air and/or printing fluid such as ink to the print head. The print head fires the ink at a print media according to a pattern electronically communicated to it through the electronics connection. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]    An example within the scope of the present disclosure is described hereinafter with reference to the drawings, in which: 
           [0003]      FIG. 1  is a side section through a page-wide array printer bar, and detached print head, according to an example; 
           [0004]      FIG. 2  is a perspective view of the printer bar of  FIG. 1 , but with the print head installed on the bar, according to an example; 
           [0005]      FIGS. 3 a  and  b    are a side section of the view arrangement in  FIG. 2 , but with a latch of the bar in a locked position, respectively unlocked (with a handle in an open position) and locked (with the handle in a closed position), according to an example; 
           [0006]      FIG. 4  is a generalised schematic representation of one example of the present disclosure, according to an example; 
           [0007]      FIG. 5 a  and  b    are cut perspective sections, just prior to final connection and in detail after final connection of the latch on the print head, according to an example; 
           [0008]      FIG. 6  is a perspective view of part of a bar and latch in an open position thereof, according to an example; 
           [0009]      FIG. 7  is the same perspective view as  FIG. 6 , but with the latch in its lockable position, according to an example; 
           [0010]      FIGS. 8 a  to  c    are detail views of a blocking mechanism to prevent actuation of a handle of the latch in the previous drawings, in an unlocked (ready to lock), locked, and unlocked (open) positions of the latch, according to an example; 
           [0011]      FIG. 9  is a schematic view in side section showing the workings of a printer bar, its latch, the handle of the latch, and a print head, of the arrangements illustrated above, according to an example; 
           [0012]      FIGS. 10A ,B and C are side sections through a latch in its lockable position, with its handle in a closed position, an intermediate position and a fully open position, according to an example; 
           [0013]      FIGS. 11 a  and  b    are side sections of details of the latch in  FIG. 10  in closed and open positions of the handle; 
           [0014]      FIG. 12  is a further detail side section of a dish plate and springs used in the latch of  FIG. 10 ; and; 
           [0015]      FIGS. 13 a  and  b    show a bistable return spring for the handle of the latch of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    In a page-wide array ink-jet printer, the position of the print head relative to the print bar must be known so that the ink is directed accurately by the print head. The print bar and print head generally have datum surfaces that, once engaged, accurately determine the position of the print head, both positionally in three-dimensions, as well as angularly in three axes. 
         [0017]    If the print heads are each considered to be essentially cubic in form, they have almost all sides already in use for different functions: their bottom surface has the print jets and is employed for firing ink at the paper or material to be printed; the sides of the print heads are closely adjacent other print heads; their back is employed for attachment to the print bar; their front for auxiliary systems (or to accommodate the next print bar); and their top for user replacement. There is no side that is obviously free for electronics connection. 
         [0018]    A latching mechanism may be used to retain the print head in place. The invention is as defined in the claims. 
         [0019]    With reference to the drawings, a page wide array printer may have a printer bar  10  across its width and on which are mounted a plurality of printer head modules  12 , also referred to herein as print heads. The modules effect the printing onto paper moving underneath the modules. They have ink jets and electronic components to control the ejection of ink from the jets, as is well known in the ink jet printing art. To reduce customer maintenance costs, the print head module is intended to be a user replaceable consumable, which means it has to offer a satisfying customer experience when replacing it. However, there are three requirements of the print head modules and their relation with the printer bar. A first is that the print heads are accurately positioned on the bar, both in terms of position in three-dimensional space, and also angularly about the three orthogonal axes. Otherwise the printer may not print accurately. The second is that there are fluid connections between the printer and the modules, for the transport of ink and air to the print heads. And thirdly there must be electrical connections so that the print instructions can be communicated from the printer to the modules. 
         [0020]    For the first purpose, the printer bar  10  and the modules  12  have mutually engaging datum faces (not shown in the drawings but schematically illustrated in  FIG. 9 ), so that, when a print head module is correctly fitted, the datum faces in the three orthogonal planes and axes ensure that the print head is properly positioned with respect to the printer bar. It is possible to arrange that a constant unidirectional force is all that is needed to press the faces together in three orthogonal directions. This can be arranged by mutually engaging ramped tracks on the bar and print-head, down which tracks the print head is pressed during installation. Gravity may be employed during fitting, but ultimately a mechanical latch, optionally with a spring bias that locks the print head in place, is necessary to secure the print head against deflection from its required position, for example by vibration in the printer during use, or paper jams or during transportation, and to return the print head after any deflection that might occur. 
         [0021]    For the second purpose, the printer bar and print head module are each provided with mutually engaging fluid connectors. These may be arranged to connect and seal by relative movement between the printer bar and print head in a linear direction. Furthermore, the fluid connector on the printer bar may include a valve, so that fluid in the conduit leading to the connector does not leak out when a module is being changed. The valve may be a check valve, which is automatically disengaged from a seat when the connection between the respective connectors is made. However, other means of connecting fluid conduits to the print head may be feasible. 
         [0022]    For the third purpose, the printer bar and print head module are each provided with mutually engaging electrical connectors. These may comprise a Peripheral Component Interconnect Express (PCIe) edge connector, which can be made and broken by relative movement between the printer bar and print head in a linear direction. 
         [0023]    Thus, turning to  FIG. 1 , the print head module  12  is shown separated from the print bar  10 , which print bar has a plurality of latches  14  hinged to the print bar about axis  16 . The print module is lowered (in the normal operating position of the printer as shown in the drawings) so that locator lugs (shown schematically at  19  in  FIG. 9 ) on a rear face  18  of the print head  12  engage in a receptor  20  on the print bar, which receptor is arranged to direct the print head into its datum position with respect to the print bar. Datum faces (shown schematically at  22  in  FIG. 9 ) position the print head, provided that a vertical force (in the direction of Arrow V in the drawings) is applied to the print head  12  with respect to the print bar  10 . 
         [0024]    The latching system  14  is the mechanism responsible for ensuring a correct connection between the print head module and the printer. This function includes the electrical (signal and power), fluidic (ink and air) and mechanical (forces) interaction. 
         [0025]    In a single bar page wide array printer with a row of several print head modules this function becomes even more critical, as the failure of any of these connections may cause a highly visible defect on the one-pass printing mode. The arrangement illustrated and described herein allows an optimal use of the real estate available on a page wide array print bar in order to ensure a reliable and easy-to-use latching system. 
         [0026]    Turning to  FIGS. 4 and 9 , latch  14  comprises a body  30  pivoted at hinge  16  to the bar  10 . The body includes a floating platform or board enclosure  32 , which is capable of movement in a direction V′, which is the vertical direction V when the latch  14  is in a lockable position of the latch as shown in  FIGS. 4 and 9 , and in  FIGS. 3 a  and  b    also. 
         [0027]    Referring specifically to  FIG. 4 , the latch  14  has a handle  34 , operatively connected to a latch member  38  and to platform  32 . The latch member  38 , when operated by a first movement of the handle, engages eye  42  on the printer bar  10  and locks the latch  14  to the printer bar. On a second movement of the handle  34 , which may be simultaneous with the first movement or subsequent thereto, platform  32  is urged with respect to the body  30  in the direction of the arrow V′. During this movement, electrical connection  60  is made between the platform and print head  12 . Fluid connections may also be made at the same time by the same movement. Once made, stud faces  110  of the platform and print head engage and press the print head  12  in the direction of the arrows V,V′ so that the datum faces  22  of the print head and print bar  10  engage and precisely locate and secure the print head with respect to the print bar, whereby the position and orientation of inkjets  21  of the print head  12  are assured. 
         [0028]    Turning to  FIG. 9 , the handle  34  here is pivoted at one end  34   a  in the body  30  about a hinge axis  36 . The other end  34   b  is user actuatable. The handle  34  has an extension  34   c  beyond its end  34   a  and hinge  36 . This is arranged to engage the latch member  38 , which is slidable against spring bias  40  in a horizontal direction substantially orthogonal to direction V. In a first movement of the handle  34  (anti-clockwise in  FIG. 9  from a fully open position of the handle) latch member  38  engages eye  42  provided on the bar  10 , so that, with the hinge  16 , the latch member  38  locks the latch  34  with respect to the bar  10 . 
         [0029]    The eye  42  is formed on a block-unlock element  44 . The block-unlock  44  is arranged to displace a block  46 , against spring bias  48 , so that latch member  38  can move rightwardly (in the direction of the arrows H in  FIG. 9 ). However, when the latch  14  is in its open position (shown in  FIGS. 1 and 2 , for instance) block  46  is able to occupy a position between shoulder  50  of latch member  38  and a stop  52  in the body  30  of the latch  14 . With the block in this position, the latch cannot move horizontally, which then prevents the handle  34  from being pivoted anticlockwise about its hinge  36 . That is, the handle  34  cannot be closed unless the block  46  is displaced (as shown in  FIG. 9 ) which only occurs in normal use when the latch  14  is pivoted to the lockable position shown in  FIG. 9  and the block-unlock element  44  engages the block  46 . The purpose of this arrangement is explained further below. 
         [0030]    Electrical interface between the latch  14  and the print head  12  takes place through a vertical PCIe connection  60 . Fluidic interface is built through vertical fluid interconnects  70 , including a primer valve  80  in the platform  32 . 
         [0031]    Platform  32  may be approximately guided for vertical movement by guides  90  in the body  30  of the latch  14 . The platform is urged by springs  92  in the direction of the arrow V (when the latch  14  is in the lockable position shown in  FIG. 9 ). The springs act against stops  94  in the body  30 . The springs  92  are illustrated as coil springs, but of course any kind of bias may be employed that performs the requisite biasing function. 
         [0032]    The platform is held with the springs compressed by the handle  34  when it is in its open position. A lever  96  is pivoted in the handle  34  intermediate its ends  34   a,b . The other end of the lever  96  is pivoted in a push bar  98  that slides in the body  30  in a horizontal direction (arrows H). At each end of the push bar is a Scott-Russel link  100   a,b  having three ends, one end (A) pivoted in the push bar, one end (B) pivoted in the body  30  and the third end C pivoted on the platform  32 . Link  100 AC is solid, whereas arm  100 B is pivoted at  97  to link  100 AC intermediate its ends. The effect of the links  100   a,b  is that horizontal movement of the push bar  98  is translated into vertical movement of the platform  32  with high gearing or leverage, so that a large movement of the handle  34  results in a small movement of the platform. This means that the springs  92  can be relatively strong without significant effort being expended in turning the handle  34 . 
         [0033]    When the latch is in the lockable position (as shown in  FIG. 9 ), and the handle is in a fully open position, the arrangement is that, as the handle is moved towards a closed position (rotated anticlockwise in  FIG. 9 ), the latch member  38  engages the eye  42  and locks the latch  14  in position. On further movement of the handle  34 , push bar  98  moves horizontally leftwardly, actuating links  100   a,b  to descend platform  32  vertically. Firstly, electrical connector  60  is made, where edge  62  of a printed circuit board in the print head  12  engages connection pins  64  of the PCIe connector pair  60 . At the same time, fluid couplings  70  (indeed, possibly several of them, if ink of different colours is connected through the latch) are made. These comprise a head fluid conduit  72 , having an O-ring  74  and a probe  76 , on the print head  12 , and a latch fluid conduit  78 , incorporating a check valve  79 , on the platform  32 . When the probe  76  enters the latch fluid conduit  78  ball  77  of the check valve  79  is displaced against the pressure of return spring  75  to open the valve and permit fluid communication between the conduits  72 , 78 . At the same time, conduits  72 , 78  are sealed by O-ring  74  between them. 
         [0034]    The fluid connection  70  between the latch  14  and the print head may comprise only an air connection, including an electrically operated pump  80  in the platform  32 . In that event, check valve  79  may be omitted. Air may be supplied on occasion to the print head to assist cleaning of the print jets. Ink connections may instead be provided directly between the print bar  10  and print head  12 . For example, print head  12  may have two pairs of downwardly directed ink ports that are adapted to engage with corresponding upstanding ports  17   a  (see  FIG. 2 ) directly on the print bar  10 . It is to be observed that a small amount of tolerance is needed in all three axes so that connections between the print head and print bar do not overcome the positioning determined by the datum system  22 . 
         [0035]    Once both electrical and fluid connections have been made, stud faces  110 A,B (optionally four pairs of them) on the platform  32  and print head  12  abut one another and when the handle  34  is fully closed, the full force of the springs  92  are applied against the print head  12  securely maintaining it in full engagement with its datum system  22 . For this purpose, an element  99  of lost motion may be provided between the end C of the links  100   a,b  and the platform  32 . Indeed, an element of lost motion may be provided at any point in the connection between the handle  34  and the platform  32  to accommodate tolerance in the engagement between the platform and print head, which may be caused by variations in the fit of the print head in the receptor  20  or any of its dimensions. The handle  34  may be provided with a clip to hold it snugly in a closed position in the latch. 
         [0036]    Thus, the mechanism translates the rotation done by the user through the handle  34  into a vertical movement of the floating platform, allowing the three connections mentioned above to be made substantially simultaneously. 
         [0037]    Referring to  FIGS. 3 a  and  b   , the arrangement is shown with the latch  14  in its lockable position, with the handle  34  open in  FIG. 3 a    and closed in  FIG. 3 b   , and in which the platform  32  can be seen separated from the print head  12  in  FIG. 3 a   , but in contact therewith in  FIG. 3   b.    
         [0038]      FIGS. 5 a  and 5 b    show the electrical connection  60  in more detail. Platform  32  includes a circuit board  120  to which a female connector  64  is attached through its connection pins  122 . The connector  64  has wire contacts  124 . Print head  12  also has a printed circuit board, carrying the components and circuits it needs, with an edge connector  62 . From this it can be seen that the edge  62  needs to be aligned with the socket  64 , otherwise damage may result to the connector  60 , either the edge  62  or the contacts  124  in the socket  64 . Indeed, a controlled entry with pure vertical (linear) movement is preferred. Consequently, it desirable that any pivoting movement of the latch  14  (about its hinge  16  to the print bar  10 ) is completed before the vertical movement of the connector  60  is effected. The same applies to the fluid connections  70 , although they are potentially less susceptible to damage. 
         [0039]    It is for this reason that the block  46  (described above) is provided. It prevents the handle  34  from being closed unless the latch is in its lockable position. It might be noted that, in the absence of the block  46 , the latch could not necessarily pivot to its lockable position with the handle  34  being in its closed position. This would likely be prevented by the latch member  38  colliding with the element  44  forming the eye  42 . Nevertheless, this would potentially damage the eye  42 , or rather the component in which it was formed, and/or the latch member  38 , bearing in mind the mass of the latch  14  and the leverage that mass has at the lock area ( 38 / 44 ), for example if the latch was dropped when at a 45 degree angle to the horizontal, the forces generated on the latch member and eye component could be substantial and damaging. This could be circumvented by, for example, providing the latch member with a ramp so that the latch member was displaced on closing of the latch, but the present arrangement is preferred because, even if the latch member did not prevent the latch from closing to its lockable position at some speed, the latch, or its connections  60 , 80  could potentially be damaged if the print head was not properly positioned in the receptor  20 . 
         [0040]    Consequently, the arrangement is such that the latch  14 , from being locked closed in the lockable position shown in  FIG. 3 b   , for example, cannot be raised without first opening the handle  34  by rotation thereof about its pivot  36  in a clockwise direction (in  FIG. 9 —anti-clockwise in  FIG. 3 b   ), whereby the platform  32  is first raised and separated from the print head  12 , disconnecting the connections  60 , 80 . Subsequently, the latch member  38  is withdrawn from the eye  42  as the handle  34  is rotated to its fully open position (shown in  FIG. 3 a   ), whereupon the latch can be pivoted open. As the latch opens, block  46  is allowed to enter the gap between latch member  38  (or a shoulder of it) and stop  52 , whereupon the latch member is then unable to move rightwardly (in  FIG. 9 ) and nor can the handle  34  close. This ensures that the platform  32  remains elevated (in the position shown in  FIG. 3 a   ). 
         [0041]    Now, should the latch be dropped from the position shown, for example, in  FIG. 6 , the latch can fall to its lockable position. No damage will be caused to the latch member or eye because the latch member is open. All that will happen is that the block  46  will be displaced, permitting the latch to be locked. Perhaps more importantly, however, with the platform  32  in its withdrawn position, any misalignment of the print head cannot cause damage to the connections  60 , 70 . 
         [0042]    Turning to  FIG. 6 , the structure of the print bar  10  can be seen where upstanding flange  140  is provided with two eyes  42   a,b , one on either side of a print head location  12 A (the print bar is not shown with all its components).  FIG. 7  shows the latch  14  in its lockable position, although it is not locked because the handle  34  is in its open position. 
         [0043]      FIGS. 8 a, b  and  c    are detailed views of latch member  38  and eye  42 . The catch member slides between guides  160  and is shown in the unlocked position in  FIG. 8 a   , and in the locked position where it engages eye  42  in  FIG. 8 b   . In both cases, the latch is in the lockable position where the eye  42 , or rather its unlock-block element  44  has displaced spring block  46 . Here, block  46  is a spring and so a separate spring  48  (as shown in  FIG. 9  is not required. 
         [0044]    In  FIG. 8 c   , the latch is open and so the spring block  46  has dropped between shoulder  38   a  of the latch member  38  and stop  52 , preventing the latch member from moving to its locked position. 
         [0045]    Electrical connections from the main body of the printer, carried in the printer bar  10 , to the latch  14 , may comprise wires that are flexed when the latch pivots about its hinge  16 . However, a possible alternative arrangement comprises contacts  116  (see  FIG. 8 c   ) extending from the board  120  within the latch  14  to contact with terminal pads (not shown) on the printer bar  10 . However, in the present arrangement, wires are used, the contacts  116  merely providing for grounding of the board  120 . 
         [0046]    An alternative arrangement is illustrated in more detail in  FIGS. 10 to 13 . Like numerals refer to the corresponding elements referred to with reference to  FIGS. 4 and 9  above. In  FIGS. 10A , B and C, handle  34  is pivoted about axis  36  from its closed position ( FIG. 10A ) through its second movement to an intermediate position ( FIG. 10B ) to its fully open position ( FIG. 10C ) after proceeding through its first movement. Thus, starting at its closed position, as handle  34  rotates clockwise, lever  96  is permitted to move from its closed position to a fully open position at the intermediate position. However, extension  34   c  as merely slid along circular abutment  37  of latch member  38  without effecting any movement thereof. It is retained in engagement with eye  42 . However, there is a change at the intermediate position. First, the lever  96  is fully open, and further movement of the handle merely allows pivot link  196  between the handle  34  and lever  96  to slide in a slot  96   a  in the lever  96 , without any further movement of the lever. Second, the extension  34   c  enters a detent  38   a  and moves the latch member  38  (leftwardly in  FIG. 10 ) to disengage it from eye  42  and unlock the latch from the print bar. Thus, in reverse, starting from the open position of the handle  34  in  FIG. 10C , its first movement closes the latch member  38  without affecting the lever  96 , and its second movement (from the intermediate position of  FIG. 10B ) actuates the lever  96  without affecting the latch member  38 . The first and second movements of the handle  34  are thus sequential in this arrangement. 
         [0047]    Turning to  FIGS. 11 a,b   , the lever  96  is pivoted in the push bar  98  about pivot  198 , and the handle  34  is shown closed in  FIG. 11 a    and in the intermediate position in  FIG. 11 b   . Push bar  98  is pivoted to modified Scott-Russel links  100 ′ a,b  about pins A′. Latch  14  has circular slots formed in its body  30  in which slide pivot pins  197  of the links  100 ′ a,b . The other ends of the links  100 ′ a,b  are pivoted about pins C′ in a dish plate  199 . Thus, horizontal movement of the push bar is translated into vertical movement of the dish plate  199 . 
         [0048]      FIG. 12  illustrates the dish plate  199  in more detail, which can be seen to mount springs  92  that abut the platform  32 . In this arrangement, when the handle  34  is open, the springs  92  are uncompressed. When the handle is closed and the platform lowered, the springs are only compressed when further lowering of the platform  32  is prevented by contact between the stud faces  110 A,B. However, with this arrangement a detent or other lock arrangement is needed to retain the handle in its closed position on the latch and maximise the bias applied to the platform  32 . For this purpose a tension spring  201  may be provided between lug  201   a  on the lever  96  and lug  201   b  on the extension  34   c  of the handle  34 , whereby a bistable arrangement as shown in  FIGS. 13 a  and  b    is provided. In the intermediate position of the handle  34 , as shown in  FIG. 13 a   , the spring  201  urges the lever  96  to its fully open position and continues to urge the handle to its fully open position ( FIG. 10C ) with the pin  196  sliding in slot  96   a . On closing the handle  34 , not only is spring  201  extended, but also springs  92  are compressed. However, on passing a cusp position when axis  36  of rotation of the handle  34  is aligned with lugs  201   a,b , tension spring  201  works against springs  92 . Because of the gearing/leverage provided by the arrangement of the links  100   a,b , push bar  98  and lever  96 , the tension spring  201  can be arranged to overcome the springs  92  and retain the handle  34  in the closed position shown in  FIG. 13   b.    
         [0049]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0050]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
         [0051]    The reader&#39;s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. 
         [0052]    Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.