Abstract:
A printing machine including a plate adapted to rotate about its axis and carrying at its periphery a plurality of object supports having a top face which receives an object to be printed and workstations distributed circumferentially around the plate in line with the trajectory of the object supports, some of which are printing stations and others of which are treatment stations. At least one of the object supports includes a lifting system which raises the object relative to the top face of the object support. The lifting system is connected to a suction head which preserves the projecting position of the object corresponding to that it initially occupied on the object support. The lifting system preferably includes at least two tubes which slide through holes through the object support and the plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to printing machines including a plate adapted to rotate about its axis and carrying at its periphery a plurality of object supports having a top face adapted to receive an object to be printed and a plurality of workstations distributed circumferentially around said plate in line with the trajectory of said object supports and some of which are printing stations and others of which are treatment stations. 
     2. Summary of the Invention 
     The invention provides a printing machine including a plate adapted to rotate about its axis and carrying at its periphery a plurality of object supports having a top face adapted to receive an object to be printed and a plurality of workstations distributed circumferentially around the plate in line with the trajectory of the object supports and some of which are printing stations and others of which are treatment stations, wherein at least one of the object supports includes lifting means adapted to raise the object relative to the top face of the object support. 
     This has the advantage that it facilitates some object treatment operations (see below). 
     The lifting means are advantageously connected to a suction head adapted to preserve the projecting position of the object corresponding to that it initially occupied on the object support. 
     The lifting means advantageously include at least one tube mounted to slide through holes through the object support and the plate. 
     The tube is preferably fastened at the bottom to a spacer fastened to a shoe adapted to cooperate slidingly with a guide rail fixed under the object support and passing through an opening in the plate. 
     To raise the object, the spacer is adapted to cooperate with fixed cam means carried by a frame of the machine having a lifting ramp and a raised position maintaining bearing surface. 
     Alternatively, the spacer is adapted to cooperate with the shoe of a lifting actuator and with a raised position maintaining bearing surface formed on the top of fixed cam means carried by a frame of the machine; as a safety feature the shoe includes a lifting ramp in case the actuator should break down. 
     The spacer advantageously cooperates with the cam means and/or the shoe via a roller. 
     The lifting means preferably include cam means and a lifting actuator and the width of the lifting ramp of the cam means is less than that of its position maintaining bearing surface whereby a cut-out is defined in which the shoe of the actuator slides. 
     A beneficial application of the above object supports is to the situation in which at least one of the treatment stations is a heat treatment station, in particular a high-temperature heat treatment station. In accordance with the invention, the object is raised at this treatment station in the direction of the heat source and the flow of heat, for drying the ink on the printed object, for example, has little effect on the object support itself or the plate, the object being treated being at a distance from them so they are not deformed by the heat, which would reduce the print quality. 
     In this type of application the end of the tube advantageously has an endpiece made from a material that is resistant to high temperatures, to prevent thermal conduction phenomena. 
     For improved thermal protection of the object support and the plate, the heat treatment station can be a high-temperature station at which there are two radially spaced screens defining a slot through which the tube passes in the raised position, the screens being halfway up the emergent travel of the tube. 
     A slot cover is advantageously adapted to cover the slot during phases in which there are no objects to be treated. 
     Another beneficial application of the above object supports is to the situation in which the objects must be turned over, for example to print both sides; in this case at least one workstation is an overturning station. 
     The overturning station advantageously includes a pallet associated with actuator means adapted to move the pallet vertically and radially and to turn it about an axis; the pallet has holding suction nozzles at the end. 
     The actuator means are adapted to insert the pallet radially into the space between the object support and the object when the object is raised by the lifting means. 
     The object supports are preferably adjustably mounted on the plate. 
     In a preferred embodiment of the invention the object support bears on a hollow rod which is externally screwthreaded and screwed into a screwthread of the plate and a screw screwed into the object support passes through the hollow rod. 
     The screwthread of the plate is advantageously an internal screwthread of a hollow screw surrounding the rod and screwed into the plate by means of a screwthread on its outside face. 
     In a preferred embodiment of the invention the lifting means comprise two sliding tubes. 
     The present invention also provides an object support for a printing machine having an object-receiving top face which includes lifting means for raising the object relative to its top face. 
     The lifting means advantageously have the features of the object support of the above printing machine. 
     To explain the invention more clearly, one embodiment of the invention, shown in the accompanying drawings, will now be described by way of purely illustrative and non-limiting example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a printing machine according to the invention. 
     FIG. 2 is a half-view partly in section and to a larger scale of the machine from FIG.  1 . 
     FIG. 3 is a view partly in section of a heat treatment station. 
     FIG. 4 is a side view relative to FIG.  3  and shows the object support raised. 
     FIG. 5 is a view to a larger scale of the bubble V in FIG.  3 . 
     FIG. 6 is a view partly in section analogous to that of FIG.  4  and shows the raising of the object support. 
     FIG. 7 is a plan view of the lifting means from FIG. 6 to a larger scale. 
     FIG. 8 is analogous to FIG.  6  and shows the object support at rest, before it is raised. 
     FIG. 9 is a partial plan view of an overturning station. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 show a printing machine  10  which has a turret  11  which rotates about a vertical axis Al on a frame  12  and carries at its periphery a plurality of object supports  22 . All this is known in the art. The turret  11  is simply a circular plate and is mounted on an indexing device  13  which is in turn mounted on the frame  12  and rotates the turret  11  stepwise. 
     The turret  11  is rotated by a motor  14  driving the indexing device  13  and conventionally associated with a gearbox  15 . 
     Workstations, in particular printing and treatment stations, are arranged circumferentially around the turret  11 , in line with the object supports  20 . 
     In this example the turret  11  rotates in the direction of the arrow F (FIG. 1) and the machine includes three printing stations  16 , three batteries  17  of heat treatment stations, a station  18  equipped with a video camera and an overturning station  19 . 
     The printing machine  10  naturally includes a feed station, not shown, for feeding objects to be treated, in line with the arrow A in FIG. 1, and an offloading station just upstream of the feed station. 
     Each battery  17  of heat treatment stations includes a heating station  171  and three cooling stations  172 . 
     The heating stations  171  are high-temperature ovens for drying printing inks deposited on the objects at the printing stations  16 . The expression “high temperature” refers to temperatures above 100° C.; drying can be effected by means of infrared lamps or hot air, for example. 
     An object support  22 , which can be seen more clearly in FIGS. 3 to  8 , has a trapezium-shaped top face  23  (FIG. 8) with a rectilinear shorter parallel side  24  perpendicular to the radius of the turret or the plate  11  passing through its middle area, two lateral sides  25  extending along radii of the plate  11 , and a curvilinear longer parallel side  26  concentric with the plate  10 . 
     To receive an object  30  to be printed, for example a square booklet, the object support  22  has a recessed housing  27  in its top surface  23  with substantially the same contour as the object  30  and containing a support plate  40 ; the bottom of the housing  27  incorporates a recess  28  adapted to be connected to a suction system. 
     The support plate  40  is not indispensable, of course, and the object can be placed directly on the top face  23  of the object support  22 . 
     If the machine incorporates a large number of stations, as is the case in the example described and shown, the plate  11  has a large diameter; it is then very difficult to achieve satisfactory flatness of the plate  11  perpendicularly to its rotation axis; to ensure that the levels of the surfaces of the thin and flat objects  30  to be printed are identical for all of the object supports  22 , the position of the supports on the plate  11  can be adjusted perpendicularly to the plate; an arrangement of this kind is described in U.S. Pat. No. 5,402,718 in particular. 
     The object support  22  (FIG. 5) bears on an abutment washer  31  which rests on a centering washer  32  which rests on the end of a hollow rod  33  which has a hexagonal handling head  34  at its other end; the abutment washer  31  and the centering washer  32  cooperate through complementary frustoconical bearing surfaces which provide some degree of ball-joint action to allow for any non-parallelism of the top face of the object support  22  and the plate  11 . 
     The rod  33  is externally screwthreaded and is screwed into an internal screwthread in the plate  11 ; the screwthread in the plate  11  is on the inside surface of a hollow screw  35  which surrounds the rod  33  and which is screwed into the plate  11  by means of a thread on its outside face. 
     The hollow screw  35  also has a handling head  36 , which is also hexagonal; the hollow screw  35  acts in the manner of an insert relative to the plate  11 ; because the latter plate is large, it is made of a light material such as aluminum, and the internal thread with which the hollow rod  33  meshes is of steel. 
     A screw  37  passes through the hollow rod  33  and the washers  31  and  32  and is screwed into the object support  22 . Its head is adapted to cooperate abutment fashion with the end face of the handling head  34  of the hollow rod  33 ; accordingly, by tightening the screw  37 , the object support  22 , the hollow rod  33  and the washers  31 ,  32  are fastened together. 
     Clearly it is sufficient to turn the hollow rod  33  relative to the hollow screw  35 , which is fixed relative to the plate  11 , to alter the vertical position of the object support  22 ; the screw  37  is tightened to lock the object support in this position. 
     Three devices like that just described advantageously ensure that the top face  23  of each object support  22  is perpendicular to the rotation axis of the plate  11 . 
     A suction head is provided under each object support  22  to retain the thin objects that it carries. This is known in the art. The suction head  39  (FIG. 5) is fastened to the bottom of the object support  22  by means of a screwthread  29  which opens into the suction recess  28 ; the suction head  39  passes through the plate  11  with clearance in a bore  38  provided for this purpose in the plate  11 . 
     Of course, when there is a support plate  40 , as in this example, it has holes for retaining the object  30  that it supports by suction. 
     According to an important feature of the present invention the object support  22  and the plate  11  have respective and aligned holes  41  and  42  (FIGS. 4 and 6) through them in which slide two tubes  43 ; the length of the tubes  43  is such that they can emerge above the surface  23  of the object support  22  and below the bottom face of the plate  11 . Of course, the support plate  40  also has holes through it through which the tubes  43  pass. 
     The lower ends of the tubes  43  which emerge under the plate  11  are fastened to a spacer  44  carrying a roller  45  at its bottom end; the spacer  44  is fastened to a skid  46 , of the ball type, for example, adapted to cooperate sliding fashion with a guide rail  47  fixed to the bottom of the object support  22  and passing through an opening  48  in the plate  11 . 
     The roller  45  is adapted to cooperate with a fixed cam  50  extending circumferentially under the plate  11 . 
     The cam  50  (FIGS. 6 to  8 ) carries an end arm  51  whose end includes a lifting ramp in the form of an inclined plane  52 ; the inclined plane  52  is narrow so that a right-angle cut-out  53  is defined at the end of the end arm  51 ; the right-angle corner of a shoe  54  attached to the head of an actuator  60  carried by a baseplate  61  fastened to the frame  12  of the machine slides vertically in the cut-out  53 . 
     The shoe  54  has at the end opposite that cooperating with the cut-out  53  a lifting ramp  55  in the form of an inclined plane  55  parallel to the inclined plane  52  of the cam  50 . 
     The inclined plane  55  of the shoe  54  extends the full width of the shoe  54 , which is very much greater than that of the inclined plane  52  of the cam  50 , and also greater than that of the cam  50 . 
     Beyond its inclined plane  52 , the top face  59  of the cam  50  extends in a plane perpendicular to the axis of the machine and constitutes a bearing surface for holding the spacer  44  in the raised position (FIGS. 3 and  4 ). 
     The cam  50  extends circumferentially in line with the batteries  17 ,  18 ,  19 ; the machine  50  therefore comprises three cams  50 . 
     The inclined plane  55  of the shoe  54  is followed by a top face  56  which is vertically aligned with the top face  59  of the cam  50  when the shoe  54  is in the position to which it is raised by the actuator  60  (FIG.  6 ), with the top face  56  of the shoe  54  also perpendicular to the axis of the machine. 
     When the shoe  54  is in the bottom position (FIG. 8) and the roller  45  is bearing on the top face  56  of the shoe  54 , the tubes  43  do not emerge from the top face  23  of the object support  22 , their end face being at most in the plane of the top face  23 . 
     In the rest position, in areas other than those in which the shoes  54  and the cams  50  are present, the assembly made up of the tubes  43 , the spacer  44  and the shoe  46  drops under its own weight toward a position defined by an abutment, not shown, and in which the lowest point of the roller  45  is practically level with the top face  56  of the shoe  54  in the bottom position, or slightly below that face  56 , and in all cases above the lowest point of the inclined plane  52  of the cam  50 . 
     Clearly, when the spacer  44  is in its top position (FIGS. 3,  4  and  6 ), the ends of the tubes  43  lift the object  30 , which is then at a vertical distance from the object support  22  carrying it and therefore at a vertical distance from the plate  11 . 
     The tubes  43  are connected to suction heads  57  to preserve the position of the object  30  relative to the object support  22 . 
     It is advantageous to provide, as in this example, the ends of the tubes  43  with an endpiece  58  made from a material that is resistant to very high temperatures, such as a fluorinated plastics material, for example. 
     The operation of the object supports  22  follows from the above description; after printing, the sequence is such that the roller  45  of the object support  22  concerned is placed at the entry of the top face  56  of the shoe  54  of the actuator  60  upstream of the heat treatment stations (FIG.  8 ), with or without the aid of the inclined plane  55  of the shoe  54 ; the suction nozzles  57  are energized and the actuator  60  is operated so that the tubes  43  lift the object  30 , because the roller  45  is then at the height of the position maintaining bearing surface  59  of the cam  50  (FIG.  6 ); as the plate  11  turns, the roller rolls on the position maintaining bearing surface  59 , which holds the object  50  in the raised position; at the end of the treatment the position maintaining bearing surface  59  is interrupted, all the raised parts descend, and the object  30  comes back into contact with the top face  23  of the object support  22 ; the descent of all the raised parts can if required be controlled by having the bearing surface  59  follow a descending ramp. 
     As shown in dashed outline in FIG. 7, the roller  45  is radially disposed so that it is in part in line with the inclined plane  52  of the cam  50 ; thanks to this arrangement, should the actuator  60  be inoperative for any reason, the plate  11 , in turning, would drive the object support  22 , and its roller  45  would then be caused to climb said inclined plane  52 , so raising the assembly and therefore the object  30 . 
     In this position of the object  30 , as already stated, the heat flux of the heat treatment station has no or very little effect on the object support  22  and the plate  11 . 
     Further heat protection can be provided, if necessary. 
     In this example, two fixed screens  62 ,  63  (FIGS. 3 and 4) are disposed in line with the heat treatment stations; they are halfway up the emergent travel of the tubes  43  and at a radial distance from each other so that a slot  64  is formed which extends in the circumferential direction and through which the tubes  43  pass in the raised position; accordingly, during heat treatment, the object  30  is above said screens  62 ,  63 , as can be seen in the figures. 
     If there is no object to be treated, it is preferable to cover the slot  64  to prevent heat escaping through it; to this end a slot cover  65  is provided and can be moved radially between two positions, namely a rest position (FIG. 3) in which the slot cover  65  is at a radial distance from the slot  64  and from the object  30  to be treated and an operational position in which the slot cover  65  covers the slot  64 . 
     Thus at rest, i.e. during sequences in which there are no objects to be heat treated, the slot  64  is covered by the slot cover  65 ; during treatment the slot cover  65  is moved radially and the slot  65  is uncovered, allowing the tubes  43  to pass through, but is masked by the object  30 ; if the instruction to uncover the slot  65  were not executed, the tubes  43  would impact on the slot cover  65  and destroy it, but it is easily replaceable. 
     Thanks to the invention, by virtue of which the object  30  is raised relative to the object support  22 , it is possible to provide a station  19  for turning over the object  30 . 
     Accordingly, a pallet  66  (FIG. 9) which has a forked end in this example is associated with actuator means adapted to move the pallet  66  vertically and horizontally, here radially, and to turn it about its axis  67 ; the pallet  66  has suction nozzles  68  at its end, four suction nozzles in this example, for holding the object  30 ; the width of the pallet  66  measured in the circumferential direction is less than the circumferential distance between the holes  41  in the object support  22 , and thus the tubes  43 , so that it is sufficient to insert the pallet  66  radially into the space between the object support  22  and the object  30  when the latter has been raised by the tubes  43  and to raise the pallet  66  vertically, which entrains with it the object  30  that is fastened to the pallet  66  by the suction nozzles  68 ; the pallet  66  is then raised vertically a sufficient distance to enable the object  30  to be turned 180°; the tubes  43  are retracted while the object is being turned over; the pallet  66  is then lowered and places the object  30  on the object support  22 .