Abstract:
An improved ink jet printing machine ( 10 ) having an object loading means ( 30 ), capable of placing an object ( 1 ) in a first standby position on a first support ( 11 ) of the machine; a pretreatment station ( 40 ), including a first object holder ( 50 ) capable of: gripping an object ( 1 ) in the first standby position; bringing it into a pretreatment position in order to allow a pretreatment device ( 41 ) to perform a pre-treatment process on the said object; and, upon conclusion of the pretreatment, bringing it into a second standby position on a second support ( 12 ) of the machine; a printing station ( 60 ), including a second object holder ( 70 ) capable of: gripping an object in the second standby position; bringing it into a printing position in order to allow an inkjet type printing device to print the desired graphic on the said object; and, upon conclusion of the printing process, transferring it to an unloading means ( 80 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims benefit of French Application No. 13 57831, filed Aug. 6, 2013, the disclosure of which is incorporated herein by reference. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of ink jet printing machines. 
       BACKGROUND OF THE INVENTION 
       [0003]    The document U.S. Pat. No. 6,135,654 discloses an ink jet printing machine. An object to be printed is placed on a belt conveyor in order to be presented successively to a pretreatment device, an ink jet printing device and a drying device. 
         [0004]    However, an ink jet printing apparatus requires a very high degree of precision in the relative positioning between the surface of the object to be printed and the ink ejection nozzles. This precision is of the order of several microns (pm). However, the use of a belt conveyor does not provide the means to achieve a such precision. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of the invention is therefore to overcome this problem by providing an improved ink jet printing machine. 
         [0006]    In order to accomplish this, the invention relates to an ink jet printing machine that is in accordance with the claims herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention and its advantages will be better understood upon reviewing the description that follows of a particular embodiment, provided purely by way of illustration and without any limitation, and with reference being made to the accompanying drawings in which : 
           [0008]      FIG. 1  is a front view of the printing machine according to a preferred embodiment; 
           [0009]      FIGS. 2 to 5  are perspective views of the machine represented in  FIG. 1 , in various different states of operation; 
           [0010]      FIG. 6  is a perspective representation of a second object holder dedicated to printing station of the machine represented in  FIG. 1 ; and 
           [0011]      FIGS. 7 to 9  represent alternative embodiments of pretreatment the device of the printing machine. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0012]    The structure of the ink jet printing machine  10  will be described with reference to  FIGS. 1 and 2 . 
         [0013]    The machine  10  provides the ability to print a graphic or a pattern directly on an object  1 . 
         [0014]    The object  1  has the shape of a circular cylinder about a main axis. The object  1  is for example a bottle. 
         [0015]    The object  1  is for example made of glass. 
         [0016]    The machine  10  comprises a frame  20  resting on foundations (not shown). 
         [0017]    The frame  20  comprises of two lateral upright posts  22  and  24 , arranged vertically, and one cross piece member  26 , arranged horizontally and supported by the upright posts. 
         [0018]    An orthonormal reference system XYZ is associated with the frame  20 . 
         [0019]    The X axis corresponds to the longitudinal axis of the cross piece member  26 . It is oriented from left to right in the  FIG. 1 . 
         [0020]    The Z axis corresponds to the vertical axis and is oriented from the bottom upwards. 
         [0021]    The Y axis is normal to the XZ plane in  FIG. 1 , and is oriented towards the rear of this figure. 
         [0022]    The machine  10  is equipped with first and second supports,  11  and  12 . In this present embodiment, the first and second supports  11  and  12  are fixed on the frame  20 . 
         [0023]    Each support has a shape that is adapted to that of the object, in a manner so as not to be in contact with the portion of the surface of the object meant to be printed. In this way, mechanical friction, which contributes to the risk of degrading the quality of the pattern printed on the object, is avoided between the support and the portion of the surface of the object meant to be printed. In the embodiment described, each support thus possesses a “V” shaped form. Such a support ensures the ability to receive an object, placed in position or taken, by approaching from above. 
         [0024]    The first support  11  defines a first standby position for an object. 
         [0025]    The second support  12  defines a second standby position for an object. 
         [0026]    The machine  10  includes, on the same side of the frame, and successively along the X axis, the object loading means  30 , a first pretreatment station  40 , a second ink-jet printing station  60  and an unloading means  80 . 
       Object Loading Means  30   
       [0027]    The object loading means  30  has the function of placing a first object  1 , on the first support  11 , in the first standby position. 
         [0028]    The object loading means  30  comprises a feeding line  31  extending horizontally, substantially parallel to the Y axis. The line  31  has lateral guide rails and a base  32  constituted by a conveyor belt  33 . The setting in motion of the conveyor belt  33 , by suitable means, ensures the ability to move an object  1  along the feed line, along the positive orientation of the Y axis. The object  1  is moved from one open end of the line  31 , located at a distance away from the frame  20 , until an end stop  34 , located at the other end of the line  31 , in the proximity of the frame  20 . The object in contact against the end stop  34  is in a reserve position. 
         [0029]    The loading means  30  comprises a gripping device  35 , of the type with suction cups, capable of moving an object from the reserve position to the first standby position on the first support  11 . The device  35  is fastened on to the upper part of the upright post  22  on the side thereof facing the line  31 . The device  35  comprises a vertical rod  36  whose lower end is provided with a suction cup  37 . A first actuating means for actuating the device  35  makes it possible to move the rod  36  vertically from the bottom upwards and vice versa. A second actuating means for actuating the device  35  makes it possible to move the rod  36  horizontally, between a position directly above the reserve position and a position directly above the first support  11 , and vice versa. 
         [0030]    By way of a variant, the object loading means comprises of other components that provide the ability to carry out an elementary operation on the object upstream of the pretreatment station. 
       First Station  40   
       [0031]    The first pretreatment station  40  includes a pretreatment device  41 . 
         [0032]    The pretreatment device  41  is a device for plasma pretreatment. It comprises a torch  42  used for carrying out a pretreatment process on one portion of the surface of an object placed so as to face the torch  32 . 
         [0033]    The device  41  is mounted on the cross piece member  26 . 
         [0034]    The device  41  is fixed along the X axis, but mounted so as to be movable relative to the frame  20  along the Z and Y axes. An adjusting means  43  provides the ability to move the device  41  along the Z axis in a manner so as to be able to adjust with precision the Z coordinate of the torch  42  at the start of each period of use of the machine  10 . A moving means  44  enables the motion of the device  41 , along the Y axis, during the pretreatment processing. In this way, the torch  42  is capable of pretreating an object on a segment oriented along the Y axis. 
         [0035]    The first station  40  includes a first dedicated object holder  50   
         [0036]    The first object holder  50  is of the socket/pin type. It comprises a fixed base socket  51  and a retaining pin  52 , that can be translated along a profiled rail  53 . 
         [0037]    The first object holder  50  comprises a clamping means to enable the movement of the pin  52  towards the socket  51  so as to clamp an object placed between the socket and the pin or away from the socket  51  so as to release an object held between the socket and the pin. The first object holder  50  is thus adapted to hold an object along a holding axis, passing through its base socket and its retaining pin. In order to ensure proper holding, the holding axis coincides with the main axis of the object being held. 
         [0038]    The first object holder  50  is mounted so that its holding axis is, at all times during the operation of the machine  10 , parallel to the Y axis. 
         [0039]    The first object holder  50  is provided with a pivot means  55  which ensures the ability to rotate the object held, about the holding axis, on a required angle and/or with a required angular velocity, in a manner so as for example, to ensure the running of the surface of the object in front of the torch  42 . 
         [0040]    The first object holder  50  is capable of performing an operative cycle consisting of the following:
       gripping an object  1  in the first standby position;   moving it in order to bring it into a pretreatment position;   moving the object by pivoting it, in order to pretreat a portion of the surface of the object;   then, upon conclusion of the pretreatment, bringing the object from the pretreatment position into the second standby position on the second support  12 , before returning empty to its operative cycle start position, in alignment with the first support  11 .       
 
         [0045]    The pretreatment position is such that the distance between the torch  42  of the device  41  and the point on the surface of the object that the torch  42  is in the process of pretreating at the current time is equal to a distance required in order for the pretreatment process to be optimal. 
       Second Station  60   
       [0046]    The second station  60  comprises an ink jet type printing device  61 . 
         [0047]    In the embodiment shown in the figures, the device  61  comprises six printing units  62 . Each unit  62  is dedicated to the printing of an elementary pattern by means of an ink having one colour specific to each unit. The pattern printed on the object results from the superposition of the elementary patterns. 
         [0048]    A unit  62  includes a nozzle (not shown) for propelling droplets of ink. A unit  62  is driven so as to propel the ink according to the elementary pattern on a portion of a surface of an object. 
         [0049]    In the embodiment described, the six nozzles are arranged in a horizontal plane XY. They are aligned along an axis parallel to the X axis and spaced apart from each other by a predetermined pitch p. 
         [0050]    The device  61  is mounted on a support arm  64  fixed on to the cross piece member  26  of the frame  20  and extending horizontally, along the Y axis, away from the cross piece member  26 . 
         [0051]    The printing device  61  is fixed along the X axis and along the Z axis relative to the frame  20 . 
         [0052]    The printing device  61  is borne on a mobile plate  65  movable along the support arm  64 . A movement means  66  provides the ability to move the plate  65  in translation along the Y axis, such that the nozzle of an active printing unit  62  is able to propel the ink droplets on an object  1  along a segment parallel to the Y axis. 
         [0053]    In the embodiment described here in detail, the second station  60  includes, downstream from the printing device  61 , a drying device  68 . This is for example an ultraviolet oven. The drying device  68  performs the function of drying the ink deposited on an object prior to its transfer to the unloading means  80 . 
         [0054]    The drying device  68  is mounted on the support arm  64 , on the side thereof opposite to the side bearing the printing device  61 . The drying device  68  is integrally secured to the support arm. 
         [0055]    The second station  60  includes a second dedicated object holder  70 . It is shown in detail in  FIG. 6 . 
         [0056]    The second object holder  70  is of the socket/pin type. It comprises a fixed base socket  71  and a retaining pin  72 , that is movable in translation along a profiled rail  73 . 
         [0057]    The second object holder  70  comprises a clamping means to enable the movement of the pin  72  towards the socket  71  so as to clamp an object placed between the socket and the pin, or away from the socket  71  so as to release an object held between the socket and the pin. The second object holder  70  is thus adapted to hold an object along a holding axis, passing through its base socket and its retaining pin. The holding axis coincides with the main axis of the object being held. 
         [0058]    The second object holder  70  is mounted in a manner such that its holding axis is parallel to the Y axis. The second object holder  70  is mounted to be parallel to the first object holder  50 . 
         [0059]    The second object holder  70  is provided with a pivot means  75  which ensures the ability to rotate the gripped object about the holding axis, on a required angle and/or with a required angular velocity, so as to ensure the running of a generatrix of the object in front of an active unit  62  of the printing device  61  or in front of the drying device  68 . 
         [0060]    The second object holder  70  further includes an auxiliary drying device  100 . 
         [0061]    This latter is mounted so as to be movable in translation along a direction parallel to the holding axis, over the profiled rail  73  for supporting the pin  72 . 
         [0062]    In a retracted position of the auxiliary drying device  100 , the second object holder  70  is capable of gripping an object placed on the second support  12 . 
         [0063]    Once the object has been gripped and held in position, the auxiliary drying device  100  is moved into an operational position, wherein it is capable of drying a portion of the surface of the gripped object. 
         [0064]    Advantageously, in its operational position, the auxiliary drying device  100  does not interfere with the printing device  61 . In this manner, the auxiliary drying device  100  may be activated so as to dry a portion of the surface of the object that has been printed, while the printing device  61  propels ink onto another portion of the surface of the object. 
         [0065]    The second object holder  70  is capable of performing an operative cycle consisting in:
       gripping an object in the second standby position on the second support  12 , and moving it to the first printing position of six successive printing positions;   sequentially moving the object from one printing position to the subsequent printing position; and   in each printing position, moving the object relative to the printing device;   moving the object from the sixth and last printing position to a drying position;   releasing the object in order to transfer it to the unloading means  80 ;   returning empty from the drying position to its initial starting position in alignment with the second support  12 , for the subsequent operative cycle.       
 
         [0072]    Each printing position is associated with a unit  62  of the printing device  61 . 
         [0073]    A printing position is such that the distance between the nozzle of the unit  62  and the point on the surface of the object that receives the ink propelled by this nozzle is equal to a distance required in order for the printing process to be optimal. 
         [0074]    A drying position is such that the distance between the drying device  68  and the portion of the surface of the object that receives the UV flux is equal to a distance required in order for the drying process to be optimal. 
       Unloading Means  80   
       [0075]    The unloading means  80  has a ramp  81  that allows, when the second object holder  70  is opened, an object to roll or slide to a discharging line  82 . 
         [0076]    The discharging line  82  extends horizontally, substantially parallel to the Y axis. The discharging line  82  includes lateral guide rails  83  and a base consisting of a conveyor belt  84 . The setting in motion of the conveyor belt  84  by suitable means ensures the ability to move an object along the discharging line  82 , in the negative orientation of the Y axis. The object is moved from one end of the line  82  located in the proximity of the frame  20  to an open end  85  located at a distance away from the frame  20 . 
         [0077]    By way of a variant, the unloading means includes other components used for performing basic operations on the object downstream of the printing station. 
       Means for Moving the Object Holders 
       [0078]    The machine  10  comprises means for moving the object holders  50  and  70 . 
         [0079]    In order to simplify the machine, the Z axis coordinates of the first and second standby positions, respectively on the first and second supports  11  and  12 , are identical and the Z axis coordinates of the pretreatment processing position, the printing positions and the drying position are identical. The travel paths of the first and second object holders  50  and  70  along the axis Z are thus identical. They are synchronised by using a common means  91  for the movement along the Z axis. 
         [0080]    The means  91  for the movement along the Z axis of the object holders  50  and  70  comprises a horizontal beam  92 , mounted to be movable between the upright posts  22  and  24  of the frame  20 . The longitudinal axis of the beam  92  extends parallel to the X axis. 
         [0081]    A single motor  93 , coupling means of the ball screw type and guide assemblies  94  for guiding the beam on each of the upright posts  22  and  24 , enable the precise movement of the beam  92 , in translation along the Z axis. 
         [0082]    The first and second object holders  50  and  70  are mounted on to the beam  92 , independently of one another. 
         [0083]    Each object holder is mounted to be movable along the longitudinal axis of the beam  92 , that is to say along the X axis. 
         [0084]    In order to do this, a means  95  for the movement along the X axis of the first object holder  50  comprises a motor, coupling means and a guide assembly for guiding the object holder over the beam. The actuating means  95  enables the precise movement of the first object holder along the beam  92 . 
         [0085]    In a similar manner, a means  98  for the movement along the X axis of the second object holder  70  comprises a motor, coupling means and a guide assembly for guiding the object carrier over the beam. The actuating means  98  enables the precise movement of the first object holder  70  along the beam  92 . 
         [0086]    In order to further simplify the machine  10 , and since the pretreatment device  41  and the printing device  61  are adjustable along the Y axis, the first and second standby positions on the supports  11  and  12  and the pretreatment position, the printing positions and the drying position are identical along the Y axis. The first and second object holders  50  and  70  therefore do not need to be moved along the Y axis. In this present embodiment, the machine  10  thus does not include means for movement in the Y axis. 
       Operation 
       [0087]    The operation of the machine  10  will now be described, initially by following the movement of the same given object  1  through the machine  10 . 
         [0088]    A given object  1  is placed at the end of the object feeding line  31 . 
         [0089]    The running of the conveyor belt  33  enables the movement of the object along the Y axis. 
         [0090]    The object  1  travels along the feeding line  31 , until coming into contact with the end stop  34  at the other end of the feeding line  31 . 
         [0091]    The object is then in a reserve position. 
         [0092]    The gripping device  35  is actuated cyclically so as to transfer an object in the reserve position to the first standby position on the first support  11 . In order to do this, while the gripping device  35  is located in an initial position in which the rod  36  is directly above the object  1  in the reserve position, the rod  36  is lowered vertically, in a manner such that the suction cup  37  comes into contact with the surface of the object  1 . A negative pressure is then applied to the suction cup  37  so as to secure the object  1  to the rod  36 . The rod  36  is subsequently raised vertically, and then moved in translation along the X axis so as to come directly above the first support  11 . The rod  36  is then lowered vertically so as to place the object  1  on the first support  11 . At this time, the balancing of the pressures in the suction cup  37  enables the releasing of the object  1  from the gripping device  35 . The rod  36  is then raised vertically. The gripping device  35  returns empty to its initial position in a manner so as to be able to take up the next object on the feeding line  31 . 
         [0093]    The first object holder  50  is moved in order to perform the following operative cycle. 
         [0094]    From an operative cycle start position in alignment with the first support  11 , the object holder  50  is actuated so as to grip the object  1 . To do this, the pin  52  is moved towards the socket  51  in order to clamp the object  1 . The object is then held in position along a holding axis oriented along the Y axis. 
         [0095]    Then, the means for the movement along the X axis and the Z axis are driven in order to, during the movement of the first object holder  50 , bring the object gripped from the first standby position on the first support  11  to the pretreatment position (shown in  FIG. 3 ). This movement takes place by combining a translation along the Z axis on a distance ΔZ and a translation along the X axis on a distance +ΔX1. The translation movement along the Z axis is obtained by a first displacement of the beam  92  resulting from the actuation of the means  91  for the movement in the Z axis, that is common to the object holders  50  and  70 . The translational movement along the X axis is caused by the actuation of the means  95  for the movement along the X axis of the first object holder  50 . 
         [0096]    The first object holder  50  maintains the object  1  in the pretreatment position for the time period during which the pretreatment device  41  performs the required pretreatment process. During this pretreatment process, the pivoting means  55  of the first object holder  50  is eventually used in order to cause the rotation of the object  1  relative to the pretreatment device  41 , in a manner such that different generatrix of the object pass in front of the pretreatment device. This movement, combined with the translation movement in the Y axis of the pretreatment device  41 , ensures the ability to pretreat an extended portion of the surface of the object. 
         [0097]    In the end of the pretreatment process, the means for the movement along the X and Z axis are driven in order to, during the movement of the first object holder  50 , move the object from the pretreatment position, to the second standby position on the second support  12  (the position shown in  FIG. 5 ). This movement takes place by combining a translational movement along the Z axis on a distance −ΔZ and a translation along the X axis on a distance +ΔX2. The Z translation is obtained by a second displacement of the beam  92  resulting from the actuation of the means  91  for the movement along the Z axis that is common to the object holders  50  and  70 . The X translation is caused by the actuation of the means  95  for the movement along the X axis of the first object holder  50 . 
         [0098]    The first object holder  50  is then actuated so as to release the pretreated object on the second support  12 . In order to do this, the pin  52  is moved away from the socket  51 . 
         [0099]    Once the object  1  has been placed in the second support  12 , the means  95  for the movement of the object holder  50  along the X axis is driven so as to bring the first object holder  50  into its operative cycle start position (shown in  FIG. 2 ). This movement takes place by bringing about a translational movement along the X axis on a distance −(ΔX1+ΔX2). 
         [0100]    The second object holder  70  is moved in order to perform the subsequent operative cycle. 
         [0101]    In its operative cycle start position, the second object holder  70  is in alignment with the second support  12  ( FIG. 2 ). It is actuated so as to grip the object  1  which is appropriately placed in position. To do this, the pin  72  is moved towards the socket  71  in order to clamp the object. The object is then held along a holding axis oriented along the Y axis. 
         [0102]    Then, the means for the movement along the Z axis and X axis are driven in order to, during the movement of the second object holder  70 , bring the gripped object from its second standby position on the second support  12 , to the first printing position (as shown in  FIG. 3 ). This movement takes place by combining a translation along the Z axis on a distance +ΔZ and a translation along the X axis on a distance +ΔX3. The Z translation is obtained by the first displacement of the beam  92  resulting from the actuation of the means  91  for the movement along the Z axis, that is common to the object holders  50  and  70 . The X translation is caused by the actuation of the means  98  for the movement along the X axis of the second object holder  70 . 
         [0103]    The second object holder  70  maintains the object in the first printing position for the time period during which the first unit prints the first elementary pattern. 
         [0104]    Then, the means  98  for the movement along the X axis, of the second object holder  70 , is driven so as to translate the second object holder  70  by a quantity corresponding to the pitch p between the first and second units  62 . Once the object is in the second printing position, the second unit is activated so as to print a second elementary pattern. Step by step, the object passes successively in front of each unit  62 . 
         [0105]    Thus, the second object holder  70  undergoes an overall translational movement along the X axis on a distance corresponding to the pitch p separating two successive units  62  multiplied by the number of intervals between the units  62  of the printing device. When the printing device comprises six units  62 , the second object holder  70  undergoes a translational movement of +ΔX4=5*p. 
         [0106]    Possibly, in each printing position, the pivoting means  75  of the second object holder  70  is used in order to cause the rotation of the object  1  about the Y axis relative to the printing device  61 , in a manner such that different generatrices of the object pass in front of the printing device  61 . This rotational movement, combined with the translational movement of the printing device  61  along the Y axis, ensures the ability to print a pattern on an extended portion of the surface of the object. This is particularly advantageous when the portion of the surface of the object that is meant to receive a pattern is of a significant length along the Y axis, which is greater than the length along the Y axis that a printing unit is able to print during a single pass. 
         [0107]    Then, the means  98  for the movement along the X axis of the object holder  70  is driven so as to move the object  1  from the sixth printing position to the drying position (shown in  FIG. 4 ). During this movement the object holder  70  undergoes a translational movement of +ΔX5. 
         [0108]    In the end of the drying process, the second object holder  70  is actuated so as to place the object on the ramp  81 . To do this, the pin  72  is moved away from the socket  71 . 
         [0109]    Once the object has been transferred to the unloading means  80 , the means for the movement along the X and Z axis are driven in order to, during the movement of the second object holder  70 , bring it back to its operative cycle start position. This movement takes place by bringing about a translational movement along the Z axis on a distance −ΔZ and a translational movement along the X axis on a distance −(ΔX3+ΔX4+ΔX5). The Z translation is obtained by the second displacement of the beam  92  resulting from the actuation of the means  91  that is common to the object holders  50  and  70 . The X translation is generated by the actuation of the means  97  of the second object carrier  70 . 
         [0110]    The object  1  placed on the ramp  81  slides or rolls along the latter to the discharging line  82 . Actuation of the conveyor belt  84  along the Y axis enables the motion of the printed object  1  away from the machine  10 . 
         [0111]    In order to increase the pace of the machine  10 , the pretreatment, on the one hand, and the printing followed by the drying, on the other hand, are performed in parallel. This refers to operations carried out in concurrent operation time mode. 
         [0112]    More specifically, while a first untreated object placed on the first support  11  is gripped by the first object holder  50 , simultaneously a second pretreated object placed on the second support  12  is gripped by the second object holder  70 . This situation is represented in  FIG. 2 . 
         [0113]    Then, the object holders are moved simultaneously in a manner so as to bring the first and second objects respectively in the pretreatment position and in the first printing position. This situation is represented in  FIG. 3 . 
         [0114]    Actuation of the means  91  for the movement along the Z axis, common to the object holders  50  and  70 , ensures the first movement of the beam  92  on which are mounted the two object holders. This first movement occurs over a distance of +ΔZ. 
         [0115]    Simultaneously, the means for the movement along the X axis of the object holders are actuated independently one from the other so as to move the first object holder  50  by a distance of +ΔX1 and the second object holder by a distance +ΔX3. 
         [0116]    Then, while the first object is in the pretreatment position, the second object passes successively into each of the printing positions, and then into the drying position. Only the means for the movement along the X axis of the second object holder  70  is then actuated so as to move the second object holder  70  on a distance of +(ΔX4+ΔX5). This situation is shown in  FIG. 4 . 
         [0117]    Then, while the first object is still in the pretreatment position, the second object is released from the second object holder  70  in a manner so as to be transferred to the unloading means  80 . 
         [0118]    Then the object holders  50  and  70  are moved simultaneously so as to bring the pretreated object, held by the first object holder  50 , into the second standby position, and simultaneously start the movement for returning the second object holder into its operative cycle start position. This situation is shown in  FIG. 5 . 
         [0119]    Actuation of the means  91  for the movement along the Z axis common to the two object holders  50  and  70  ensures the second movement of the beam  92 . This second movement occurs over a distance of −ΔZ. 
         [0120]    Simultaneously, the means for the movement along the X axis of the first object holder  50  is actuated, and the first object holder  50  is moved by +ΔX2. 
         [0121]    Then, the first object holder  50  is actuated so as to release the pretreated object that it holds, to place it on the second support  12 . 
         [0122]    Finally, the object holders  50  and  70  are moved simultaneously so as to bring the first object  50  into its operative cycle start position and the second object holder  70  into its operative cycle start position. 
         [0123]    The means  95  and  98  for the movement along the X axis of the object holders are actuated independently of each other. The first object holder  50  is moved by a distance of −(ΔX1+ΔX2). The second object holder  50  is moved by a distance of −(ΔX3+ΔX4+ΔX5). 
         [0124]    The person skilled in the art will understand that, by dedicating an object holder to the ink jet printing station, the precision required for high quality printing can be achieved. 
         [0125]    The addition of a pretreatment processing step upstream of the printing station makes it possible to increase the pace. 
         [0126]    The choice, through construction or by adjustment, of the positioning of each device provided on the machine makes it possible to reduce the number of movement means and/or provide to share some of the movement means required for the movements of the two object holders. 
         [0127]    Numerous alternative embodiments of the machine are possible, in particular with respect to the positioning and the relative movements of the various devices or equipment units in relation to each other. 
         [0128]    In the embodiment shown in  FIGS. 1 to 5 , the pretreatment device  41  is a device for pretreatment using plasma torch. 
         [0129]      FIGS. 7 to 9  show alternative embodiments of the pretreatment device. In these figures, only the operational part of the pretreatment device is represented, whereas the object  1  to be pretreated is held in the pretreatment position by the first object holder  50 . 
         [0130]    In  FIG. 7 , the pretreatment device is a device for flame pretreatment . The burner  142  enables combustion of a fuel, supplied from a source through the channel  143 , with the oxygen in the ambient air, detected and captured by the means  144  for generating a row along the axis Y, of flames  145 . 
         [0131]    In  FIG. 8 , the pretreatment device is a device for Corona pretreatment. It comprises a head  342  provided with a plurality of electrodes for the application of appropriate electrical discharges on the surface of the object to be treated. 
         [0132]    Finally, in  FIG. 9 , the pretreatment device is a device for chemical pretreatment. The applicator  442  includes a felt pad  445  capable of being soaked with a liquid chemical product and applied against the portion of the surface of the object  1  to be pretreated. The applicator  442  includes a dropper  444  to be used to soak the pad with an appropriate flow of drops. The applicator  442  includes a button  443  for adjusting the pressure of application of the felt pad  445  on the object. 
         [0133]    By way of various different pretreatment processes that it is possible to implement upstream of the printing station, the ink jet printing machine is universal. 
         [0134]    In the embodiment described in detail here above, the object to be printed is cylindrical. Once it is placed in the printing position associated with a printing unit, the object is rotated about itself, in a manner so as to cause a portion of the object to be printed to run in front of the active printing unit. To do this, the second object holder is provided with a pivoting means  75 . Furthermore, the printing unit may be displaced parallel to the pivoting axis so as to extend the portion of the surface of the object that is printed. 
         [0135]    As an alternative, the object to be printed is flat. It is placed in a printing position associated with a printing unit, in a manner such that its planar surface is parallel to an XY plane. The object is then moved in translation relative to the printing unit along the X direction, in a manner so as to cause a portion of the object to run in front of the printing unit. To do this the second object holder is provided with a means for translation movement along the X axis. Advantageously, the printing units of the printing device being aligned along the X axis, the means for enabling the translation of the object in front of the printing unit is constituted by the means  98  for the movement along the X axis of the second object holder. More advantageously, the movement of the object in front of each printing unit as well as the movement of the object from one unit to another take place in a continuous manner, with the second object holder being driven at a constant speed along the X axis. 
         [0136]    Furthermore, still according to this alternative relative to a flat object, whereas the object is placed in a printing position associated with a printing unit, the latter may be translated relative to the frame along the Y axis, in a manner so as to cause an extended portion of the object to run in front of this printing unit. To do this, the printing device is provided with a means for enabling translation along the Y axis, identical to the movement means  66  described in detail here above.