Patent Publication Number: US-6337487-B1

Title: Ultraviolet radiation drying oven and printing machine including at least one such drying oven

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally concerned with ultraviolet radiation drying ovens of the type used when the product to be dried is a synthetic product which must be polymerized to dry it. 
     It is more particularly directed, but not necessarily exclusively so, to the situation in which a drying oven of the above kind is designed to be fitted to a printing machine including a turret which is mounted to rotate about its axis and which carries, radially, at its periphery, a plurality of object-carrier supports which are themselves mounted to rotate on the turret, and at least one workstation which is fixed and past which the object-carrier supports move. 
     2. Description of the Prior Art 
     When, as is usually the case, the object to be treated must be printed several times in succession with different colors, a plurality of workstations is in practice circumferentially distributed around the axis of the turret; most of them are printing stations, although the first one can be a varnishing station, with at least one drying oven downstream of each workstation in the direction of rotation of the turret. 
     If the drying oven is an ultraviolet radiation drying oven, it usually includes a chamber containing the necessary lamp with a localized opening, through which the radiation passes, in line with the path of the object-carrier supports. 
     With an ultraviolet radiation drying oven of the above kind the problem arises of confining the radiation within the corresponding chamber. 
     Otherwise, this radiation could affect the operation of the adjacent workstation, causing premature and therefore untimely polymerization of the product used at that station. 
     This is the case in particular if a workstation is a screenprinting station. 
     If unintended ultraviolet radiation reaches a printing station of this kind, there is the risk of the mesh of the corresponding screen becoming progressively clogged. 
     To alleviate this drawback, it has been proposed to add a cover to the drying oven which, extending laterally on either side of the drying oven, forms a kind of corridor for the object-carrier supports, along which the object-carrier supports move before reaching the drying oven and after leaving it. 
     There is therefore always at least one object-carrier support between the chamber of the drying oven and the entry and exit of the corridor and this intercepts the corresponding radiation and prevents it being propagated to the outside. 
     However, the footprint of a cover of the above kind on the working area of the machine is large, which is to the detriment of its capacity in terms of workstations. 
     It has also been proposed to associate with the opening in the chamber of an ultraviolet radiation drying oven of the above kind a mask mounted to move between a closed position in which it interferes with the opening and an open position in which it exposes it. 
     Apart from the fact that prior art implementations of this kind are generally bulky at the present time, they are all always relatively complex and are not totally effective. 
     At present there usually remains a transient period during which, having to move from its closed position to its open position to allow an object-carrier support to pass it, the mask allows the radiation it has to intercept to filter out, at least momentarily. 
     A general object of the present invention is an arrangement which avoids these drawbacks. 
     SUMMARY OF THE INVENTION 
     To be more precise, the invention consists in an ultraviolet radiation drying oven including a chamber containing the necessary lamp and which has a localized opening for the radiation to pass through and, associated with the opening, a mask mounted to move between a closed position in which it interferes with the opening and an open position in which it exposes it, in which oven the mask is mounted to rotate relative to the chamber, is divided into two shutters in diametrally opposite positions and is associated with a second mask which is also divided into two shutters, is coaxial with the first mask and, like the first mask, is mounted to rotate relative to the chamber with a motion that is the converse of that of the first mask. 
     Because of the features of the invention, the footprint of the drying oven on the working area of the machine to which it is fitted is hardly greater than that of an object-carrier support, since it is sufficient for the rotary masks that it includes, in accordance with the invention, to be able to closely surround an object-carrier support of this kind. 
     The capacity of the machine, in terms of the number of workstations, can advantageously be increased commensurately. 
     Furthermore, because of the simultaneous use of two masks operating in opposite directions, propagation of radiation to the outside is prevented at all times, without any transient period during which radiation could escape. 
     The features and advantages of the invention will emerge from the following description which is given by way of example and with reference to the accompanying diagrammatic drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a printing machine fitted with ultraviolet radiation drying ovens in accordance with the invention. 
     FIG. 2 is a partial view of the printing machine in axial section, in line with one of the drying ovens and to a larger scale. 
     FIG. 3 is a partial elevation view of the drying oven as seen in the direction of the arrow III in FIG.  2 . 
     FIG. 4 is a partial view of it in cross section taken along the line IV—IV in FIG.  2 . 
     FIGS. 5A,  5 B and  5 C are partial views in axial section which are derived from that of FIG.  4  and show various successive phases of operation of the corresponding masks. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The figures show, by way of example, the application of the invention to a printing machine  10  including at least one workstation  11 A,  11 B associated with at least one drying oven  12 . 
     Because the printing machine  10  is not of itself relevant to the present invention, it will not be described in detail here. 
     Only its component parts necessary to an understanding of the invention will be described. 
     In the embodiment shown, the printing machine  10  includes a circular contour turret  13 , which is mounted to rotate stepwise about its axis A 1  and which carries, radially, at its periphery, a plurality of object-carrier supports  14  which are themselves mounted to rotate on the turret  13  about axes A 2  orthogonal to its axis A 1 , and a plurality of fixed workstations  11 A,  11 B and past which the object-carrier supports  14  move, there being a drying oven  12  downstream of at least one of the workstations  11 A,  11 B, in the direction of rotation of the turret  13 , and in practice there is an oven downstream of each workstation  11 A,  11 B. 
     In the embodiment shown, the workstations  11 A,  11 B are preceded by a loading and offloading station  15  and by a flame treatment and dust removal station  16 . 
     As shown here, for example, workstations  11 A,  11 B include a varnishing station  11 A and a plurality of printing stations  11 B. 
     In the embodiment shown, the printing stations  11 B employ the screenprinting process. 
     Finally, in the embodiment shown, the object-carrier supports  14  are simple mandrels, the objects  18  to be printed being simple flexible tubes which merely have to be threaded over such mandrels, as shown diagrammatically in chain-dotted line for one of them in FIG.  2 . 
     All the drying ovens used are identical. 
     They are ultraviolet radiation drying ovens. 
     As seen best in FIG. 2, and in a manner that is conventional in itself, a drying oven  12  of this kind includes a chamber  20  containing the necessary lamp  21  and having a localized opening  22 , facing the path followed by the object-carrier supports  14 , through which the radiation passes and, associated with the opening  22 , a mask  23  mounted to move between a closed position in which, as shown in FIGS. 2 and 4, it interferes with the opening  22  and an open position in which, as shown in FIG. 5B, it exposes it. 
     In accordance with the invention, the mask  23 , which is mounted to rotate relative to the chamber  20  about an axis A 3  that is radial relative to the turret  13 , is divided into two shutters  23 A,  23 B in diametrally opposite positions and on respective opposite sides of the axis A 3  and is associated with a second mask  24  which is also divided into two shutters  24 A,  24 B, is coaxial with the first mask  23  and, like the latter, is mounted to rotate relative to the chamber  20 , with a motion contrary to that of the first mask  23 . 
     In the embodiment shown, the chamber  20  has two parts  20 A,  20 B separated from each other, namely a top part  20 A and a bottom part  20 B, and the two parts  20 A,  20 B define between them a slot  25  in which the object-carrier supports  14  move and the masks  23 ,  24  operate. 
     As shown here, for example, the lamp  21  is in the top part  20 A of the chamber and the corresponding opening  22  is in the bottom part of the top part  20 A. 
     Alternatively, however, the lamp  21  can equally well be in the bottom part  20 B of the chamber  20 , in which case the corresponding opening  22  is formed by the top part of the bottom part  20 B. 
     As shown here, for example, the chamber  20  is generally parallelepiped-shaped and the opening  22  in the bottom part of its top part  20 A extends only a portion of its width, in the middle part thereof. 
     The drying oven  12  as a whole is elongate along a radius of the turret  13  and likewise the axis A 3  of its masks  23 ,  24 . 
     The lamp  21  is itself elongate along this radius and, as shown here, a reflector  27  is preferably associated with it to focus its radiation onto the top generatrix of the object-carrier supports  14 . 
     The design is such that when an object-carrier support  14  is vertically aligned with the lamp  21 , its axis A 2  is aligned with the axis A 3  of the masks  23 ,  24 . 
     As in the embodiment shown, the shutters  23 A,  23 B,  24 A,  24 B of the masks  23 ,  24  preferably each extend in a circular arc about the axis A 3  of the assembly. 
     As shown here, for example, each of the shutters  23 A,  23 B,  24 A,  24 B of each mask  23 ,  24  extends along a circular arc subtending an angle at the center close to 90°. 
     To be more precise, in the case of one of the masks  23 ,  24 , here the radially outermost mask  23 , the shutters  23 A,  23 B each extend along a circular arc subtending an angle at the center slightly greater than 90° and, in the case of the other mask  23 ,  24 , here the radially innermost mask  24 , the shutters  24 A,  24 B each extend in a circular arc subtending an angle at the center substantially equal to 90°. 
     Accordingly, in the closed position shown in FIG.  4  and the open position shown in FIG. 5B, the shutters  23 A,  23 B of the outer mask  23  each project on either side of the respective shutters  24 A,  24 B of the inner mask  24 , and in the intermediate positions shown in FIGS. 5A and 5C the shutters  23 A,  23 B of the mask  23  each slightly overlap the respective shutters  24 A,  24 B of the mask  24  at each end. 
     As in the embodiment shown, the two circumferences CA, CB along which the shutters  23 A,  23 B,  24 A,  24 B of the two masks  23 ,  24  extend are preferably near each other, to minimize the overall size of the assembly. 
     In the embodiment shown, the two shutters  23 A,  23 B of the mask  23  are in practice fastened to a sleeve  28  mounted to rotate in a fixed bush  29  and extend cantilever-fashion from the sleeve  28 . 
     Likewise, the two shutters  24 A,  24 B of the mask  24  are fastened to a block  30  which is attached by a screw  31  to the end of a shaft  32  mounted to rotate in the previously mentioned sleeve  28  and extend cantilever-fashion from the block  30 . 
     Parallel to the axis A 3  of the assembly, the shutters  23 A,  23 B,  24 A,  24 B of the two masks  23 ,  24  are sufficiently long to extend either side of the lamp  21 , extending largely beyond it. 
     As in the embodiment shown, the two masks  23 ,  24  are preferably operated synchronously. 
     As shown, for example, the two masks  23 ,  24  share the same drive system  34 . 
     In the embodiment shown, the drive system  34  includes an actuator  35  whose body  36  is articulated at a fixed point  37  and whose piston rod  38  is articulated to a swing-arm  39  which is in turn mounted to pivot about a fixed point  40  in its middle area. 
     A first link  41  is articulated to the swing-arm  39  and to a flange  42  fastened to the sleeve  28 , at a point  43  on the flange  42  which is eccentric to the axis A 3  of the assembly. 
     Likewise, a second link  44  is articulated to the swing arm  39 , on the side thereof opposite the articulation of the first link  41 , and to a flange  45  fastened to the shaft  32 , at a point  46  on the flange  45  which is eccentric to the axis A 3  of the assembly. 
     Assume firstly that, as shown in FIGS. 2 and 4, the two masks  23 ,  24  are in the closed position and, as shown in continuous line in FIG. 4, an object-carrier support  14  reaches the immediate vicinity of the drying oven  12 . 
     In this closed position, the shutters  23 A,  24 A of the masks  23 ,  24  are superposed on each other and globally extend from one to the other of the two radial edges of the opening  22  in the chamber  20  of the drying oven  12 , and therefore intercept the radiation from the lamp  21 . 
     The turret  13  advancing by one step, as symbolized by the arrow F 1  in FIGS. 4 and 5A, the object-carrier support  14  is engaged in the slot  25  formed by the two parts  20 A,  20 B of the chamber  20 , until it is vertically aligned with the lamp  21 , as shown in chain-dotted line in FIG.  4  and in continuous line in FIG.  5 A. 
     The two masks  23 ,  24  are then rotated and, as follows from what has been described above, the mask  23  turns in a first direction, for example the clockwise direction, as shown by an arrow F 2  in FIG. 5A, and the mask  24  turns in the opposite direction, and therefore the counterclockwise direction here, as symbolized by an arrow F 3  in FIG.  5 A. 
     In practice, after their shutters  23 A,  23 B,  24 A,  24 B move to an intermediate position in which, as shown in FIG. 5A, they entirely surround the object-carrier support  14 , the rotation of the masks  23 ,  24  is continued as far as their open position in which, as shown in FIG. 5B, their shutters  23 A,  23 B,  24 A,  24 B, which are again superposed, expose the opening  22  which is vertically in line with the lamp  21 , the shutters  23 A,  23 B,  24 A,  24 B then interfering with the slot  25  formed by the two parts  20 A,  20 B of the chamber  20 , extending globally from one of these parts  20 A,  20 B to the other one. 
     The object-carrier support  14  is then rotated about its axis A 2 , which at this time is coincident with the axis A 3  of the masks  23 ,  24 , to dry the object  18  (not shown) that the object-carrier support  14  is assumed to be carrying. 
     This rotation can continue over one or more turns. 
     After a rotation of the masks  23 ,  24  which is the opposite of the previous one, as symbolized by the arrows F′ 2  and F′ 3  in FIG. 5C, and after their shutters  23 A,  23 B,  24 A,  24 B have moved to an intermediate position in which, as previously, and as shown in FIG. 5A, they again entirely surround the object-carrier support  14 , the masks  23 ,  24  are returned to their original closed position, FIG. 4, and, the object-carrier support  14  being therefore released, the turret  13  again advances by one step, as symbolized by a chain-dotted arrow F 4  in FIG.  5 C. 
     Likewise, a new object-carrier support  14  is then vertically aligned with the chamber  20 , with its axis A 2  aligned with the axis A 3  of the masks  23 ,  24 . 
     Operation then continues cyclically in the same manner as previously. 
     Of course, the invention is not limited to the embodiment described and shown, but encompasses any variant execution thereof.